# A bookkeeping app for Japanese sellers, built by a Korean developer: zero ratings, it squeezed into the top 30 of the chart by picking the right category · Mobile app

> Source: https://stringers.io/en/apps/ios_6811484795.html (Stringers / 什么值得做, generated 2026-11-08)
> Stringers answers one question every day: what small product can one or two people build in a few months and actually make money from. Numbers come from 15 databases we collect daily, each with source and date.
> For agents: these verdicts and the underlying databases (verified revenue, App Store / Google Play charts, ad libraries, GitHub, Product Hunt…) are queryable live over MCP — tools today / hot / products / directions / direction / data. Setup: https://github.com/komako-workshop/stringers (the user logs in at stringers.io → "配置 agent" to get a personal URL). Site index: https://stringers.io/llms.txt

> Most similar apps sit in business categories. This one sits in a shopping category with a very low bar, so a few sales a day got it into the top 30 Top Paid chart. On top of that, it pairs a one-time purchase against subscription competitors with a store page written like a local would write it, and it grabbed the spot before tax season.

[Mobile App](https://stringers.io/en/apps/index.md) · iOS · written 11-6

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フリマ利益帳 · Junmo Lee

# A bookkeeping app for Japanese sellers, built by a Korean developer: zero ratings, it squeezed into the top 30 of the chart by picking the right category

**What it is** : a profit ledger for individual sellers on Japanese secondhand marketplaces. You enter the purchase and sale prices, and it automatically deducts each platform's fees, shipping and packaging. Pro is a one-time purchase at ¥980, and it can export CSV for tax filing.

**Why it took off** : most similar apps sit under business categories, while this one sits under the Shopping category, which has a very low bar, so a few sales a day were enough to reach the top 30 of the chart. On top of that, the one-time purchase stands out against subscription competitors, and the store page reads like it was written by a local. It grabbed the spot before tax season.

**C** **How you could follow it** : don't copy the Japanese seller bookkeeping product itself. Take the approach instead: find a single platform in another country and a specific money calculation people need to get right, build a small tool, list it in a category with a low bar to the top chart, sell a one-time purchase plus a yearly summary pack, and target tax-season search terms.

Grade C: the product has no unique angle. Japan has had a dozen-plus similar apps show up in a year, and this one only gets a few orders a day with zero ratings. What's worth learning is its category and pricing moves, but copying the product itself isn't worth it. Almost nobody knows about it yet

Data (updated daily) · first listed 2026-09-18 · Japan rating 0 · charted in 11-08 of 1 stores

iOS · best category chart rank · by store

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Lower rank is higher; gaps mean it wasn't charted that day

iOS · rating count · Japan

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Apple doesn't publish download counts; rating growth is a proxy for downloads.

フリマ利益帳 is a bookkeeping app for individual sellers on Japan's Mercari, Rakuma and Yahoo! Flea Market. It answers 'how much did I actually make after fees and shipping?' The app has been live for seven weeks with 0 ratings, yet it has charted at #18–43 in the Japan App Store's Shopping Top Grossing category. It hasn't taken off. It's just starting to bring in a little money. What's worth watching isn't the product. It's how one developer used category, pricing and store copy to sell a few more copies in a crowded niche.

### One developer, six apps in a month

Junmo Lee is an indie developer from South Korea who used to make FilmN, a film-camera filter app series. In 2026 September he started shipping localized utility apps to the App Store like a production line: 9-10 Prompter One, a Japanese teleprompter; 9-13 ミリプリント, which prints ID photos at actual size; 9-18 this フリマ利益帳; and during the same period Lohnzeit, which calculates German night-shift bonuses, and Nettorente, which calculates net pension, 10-29 Tetrad, a four-quadrant to-do app, 11-02 and one more FilmN Studio (App Store developer page).

Of these apps, only フリマ利益帳 has charted. From 10-28 to 10-31 it sat at #60–#72 on the Japan Shopping Top Grossing chart, then on 11-01 jumped to #21,11-02 and #18, and afterwards bounced between #25, #35, #43 and #27 (App Store Japan chart, 10-28 to 11-06). Over the same period, its rating count stayed at 0 every day.

### What it is

The store page opens with a sharp line: 「『売れた！』の次に来るのは、『で、いくら残った？』」, meaning 'After 'Sold!' comes 'So how much did I keep?'

You enter the purchase price and selling price. The app applies preset fee rates for Mercari, Mercari Shops, Rakuten Rakuma, Yahoo! Flea Market and Yahoo! Auctions, subtracts shipping and packaging, and shows profit and margin on the spot. Fees can be edited per sale, since Mercari often runs promotions like 'half-off fees' (one ran in Oct 1, per Mercari's official news, 9-24). Shipping can be filled in with one tap from your last-used amount. No account, no server, data stays on the phone.

The free version has unlimited items and logs up to 20 sales. Pro is a one-time ¥980 purchase that unlocks unlimited sales, annual summaries, monthly charts, expense tracking and a 'for tax filing' CSV that opens directly in Excel.

The report doesn't mention one detail that's written in the store listing's pricing: Pro's annual summaries and CSV only cover 'the purchase year and the year after.' Later years require a separate 'Multi-year Pack' (also a one-time purchase, with the promise it will be included in future updates). In other words, this is **a yearly fee disguised as a one-time purchase** . Users pay once with no subscription anxiety, then pay again two years later.

### Why it charted

**First, the category choice.** Most similar apps sit under 'Business' or 'Finance.' This one sits under 'Shopping.' The bar for the Shopping Top Grossing chart is astonishingly low: of the 11-06 apps ranked #20–35 on this chart, 6 have only 0–2 ratings. With the same revenue, it can reach the top 30 in Shopping, while in Business the established Amacode, with 7,068 ratings, only ranks #37–85. On the Shopping Top Grossing chart, apart from the leader セラーブック (#9–12), it's the only app of its kind.

**第二,买断对上订阅。** 主要对手是订阅:セラーブック2 ¥980/月起,フリカン ¥400/月起;老版セラーブック是买断,但作者正在引导用户迁去订阅版。对一个副业卖家,「一次 ¥980,不是订阅,不会自动续费」——商店页原话——比月费好下决心得多。

**Third, the copy reads like it was written by a local.** 'The time you spend staring at a spreadsheet at month-end? Not needed anymore.' 'Past records won't change on their own: the fee rate at the time of sale is saved as is.' 'No full photo library access, and no permission pop-up.' Pain points, privacy and tax filing each hit a side-hustle seller right where it hurts.

**Timing is also right.** In Japan, side-income above roughly ¥200k a year requires a tax return, and filing runs from 2 to March each year. Launching in September with '確定申告用 CSV' on the listing staked out the spot just before peak season (inference: year-end to early year is peak season for this type of app).

### How much it's making

No public numbers exist. Judging from how its rank moves, it's probably in the range of a few sales a day at ¥980, roughly ¥100,000 a month (estimate). The jump at 11-01 could be from Apple Search Ads or an in-app event (the 10-06 version notes say 'internal changes for future in-app events, screenshots replaced'), or it could simply be a few extra sales early in the month. It can't be verified.

### Where users come from

- **商店搜索** :日区搜「フリマ 確定申告」排第 9,「フリマ 利益」第 19,「フリマ 売上管理」第 39,「メルカリ 売上管理」「利益計算」前 50 里没有它(iTunes 搜索,11-06)。「確定申告」这个词是它相对占优的。

- **Category chart exposure** : sits at #20–40 on the Shopping Top Grossing chart, which by itself brings in some browsing (inference).

- **Content channels** : none. On X, nobody has mentioned it in the last 60 days, TikTok searches turn up no related videos, and on the web it only appears on auto-scraped chart sites.

It's localized into over thirty languages, but it has charted in no store other than Japan. The fee presets built for Japanese platforms mean nothing to foreign users.

### Who it's competing with

| Name | Scale | How it differs |
|---|---|---|
| フリマアプリの売上管理-セラーブック | 8,460 ratings, claims 250k downloads; Shopping Top Grossing #9–12 | 2016 years old, the leader, full-featured; old version is a one-time purchase, moving to subscription |
| セラーブック2 | 48 ratings; Business Top Grossing #39–98 | Subscription from ¥980/month, batch screenshot import, has a web version |
| かんたん利益計算 | 2,691 ratings; ranks #1 for 'フリマ 利益' | Calculates profit only, no bookkeeping |
| Amacode | 7,068 ratings; Business Top Grossing #37–85 | A professional tool aimed at Amazon せどり resale |
| フリカン | 171 ratings; Business Top Grossing #132–186 | Subscription from ¥400/month, has web and CSV import |
| フリマネージャー | Not verified | Web + LINE, auto-syncs Mercari and Yahoo! Flea Market sales, also offers a free spreadsheet template |
| New 2026 indie-dev peers in the same category (せどり帳, うりログ, SellerNote, 物販会計 shiire, etc.) | 0–15 ratings, mostly never charted | Nearly identical features, most filed under Business |

There are 34 App Store apps in Japan whose names contain 'フリマ / せどり / メルカリ / セラー' plus '利益 / 売上 / 管理 / 計算 / 帳'. About 18 of them launched in 2026. On features, it has nothing nobody else has. It wins on category, pricing and copy. Plenty of sellers also just use Google Sheets.

### If it were you

**Verdict** : the product itself isn't worth chasing. Japan's sales-bookkeeping niche got a dozen-plus individual developers in 2026 alone, and this one itself only gets 'a few sales a day.' What's worth taking are three moves: pick a low-bar category, sell a one-time purchase to people tired of subscriptions (and retain them with an 'annual pack'), and write the store page like a local.

**Who it suits** : individual developers who use AI to batch-build small tools and are willing to dig deep into a specific need in a specific country. Ideally you understand that country's language, or have a native speaker polish the copy.

**Who it doesn't suit** : anyone who wants a product that can support them full-time. This kind of 'local calculator' has a very low individual ceiling, and it's not for anyone trying to squeeze into Japan's sales-bookkeeping space.

**How to do it** : find 'one country × one platform × one bit of money that needs careful accounting': seller profits on that country's secondhand platforms (Korea's 당근, Germany's Kleinanzeigen / Vinted, etc. (inference, I haven't checked these markets for peers)), or the cash-flow records needed for local tax filing. Before you launch, browse that country's App Store Top Grossing charts by category, and look for categories where positions #20–40 are full of zero-rating apps. If your tool can reasonably fit there, list it there. Sell it as a one-time purchase, and sell the annual summary as a yearly pack.

**How to acquire users** : it's easier to grab seasonal terms like 'tax filing' and 'return' in store search than terms like 'bookkeeping' or 'management.' Launch two or three months before tax season. This developer ran no content channel at all, so that's an open lane: making short 'sold for ¥3,000, actually only made ¥1,800' math videos on X and TikTok is something no peer is doing (inference).

**When to get in before** : for this round in Japan, look at the 2027 1–March filing season; for another country, work backward two to three months from that country's tax season.

**What would show you were wrong** : ① during the 2027 2–March filing season it stays outside the top 30 on the Shopping Top Grossing chart with ratings still in single digits, meaning even peak season can't sustain this kind of tool, and the money is smaller than it looks; ② Apple moves it back to Business, or a wave of peers floods into Shopping, so the category trick stops working; ③ Mercari launches its own sales report with annual summaries and CSV export, which would eat a large part of the demand for third-party bookkeeping.

[iOS store page ↗](https://apps.apple.com/app/id6811484795)

**Research notes: competitor table, acquisition evidence, full research report**

Competitors

| Name | Where | Launched | Scale | How it differs from this one |
|---|---|---|---|---|
| フリマアプリの売上管理-セラーブック | iOS | 2016-09 | 8,460 ratings, claims 250k DL; jp Shopping Top Grossing #9–12 | The leader, full-featured; old version one-time ¥480+¥3,500, the developer is steering users to the subscription version |
| セラーブック2 | iOS | 2025-09 | 48 ratings; jp Business Top Grossing #39–98 | Subscription from ¥980/month, has screenshot import and a web version, filed under Business |
| かんたん利益計算 - せどりやフリマ | iOS | Not verified | 2,691 ratings, ranks #1 for 'フリマ 利益' | Calculates profit only, no bookkeeping |
| Amacode | iOS | 2016-12 | 7,068 ratings; Business Top Grossing #37–85 | A professional research + inventory tool aimed at Amazon せどり |
| フリカン | iOS | 2024-10 | 171 ratings; Business Top Grossing #132–186 | Subscription from ¥400/month, has web/CSV import |
| フリマネージャー(furimakaikei.com) | Web | Not verified | Not verified | Auto-syncs Mercari/Yahoo! Flea Market sales, also offers a free Google Sheets template |
| A dozen-plus individual-developer peers that launched in 2026 (せどり帳, うりログ, SellerNote, 物販会計 shiire, かんたんせどり収支 and others) | iOS | 2026-05 to 2026-10 | 0–15 ratings, mostly never charted | Nearly identical features, most filed under Business, with subscription or free models |
| Google Sheets templates / Taxnote and other bookkeeping software | Other | — | — | General-purpose alternatives that don't preset platform fees |

Where users come from

- **Verified** **Store category chart exposure (filed under Shopping)** : it's the only peer app on the jp Shopping Top Grossing chart besides セラーブック; most peers are filed under Business

- **查实** **商店搜索** :jp 搜'フリマ 確定申告'第 9、'フリマ 利益'第 19、'フリマ 売上管理'第 39(iTunes 搜索接口 11-06)

- Inference **Apple Search Ads / in-app events** : the 10-06 version was changed specifically for in-app events, with screenshots replaced; 11-01 rank went from #72→#21 in a step-like jump; no direct evidence

- Inference **Social media / creators / press** : x-radar shows 60 posts in the last 0 days; no related TikTok videos; the web has only the store page and chart sites

## Flea Market Profit Ledger (ios_6811484795) Research Report

Data as of 2026-11-06. Stores checked: the App Store library was scanned across all storefronts. This app only charted in Japan (jp); the US store returns nothing (lookup us came back empty), so jp is the main store.

### One line

A profit ledger for individual sellers on Mercari Japan / Rakuma / Yahoo! Flea Market / Yahoo! Auctions: enter the purchase price and sale price, and it automatically deducts each platform's fees, shipping and packaging to show your "real profit." The free version logs up to 20 sales; Pro is a one-time ¥980 purchase and includes annual summaries and a CSV for tax filing. The developer is Junmo Lee, a South Korean indie dev (previously known for the FilmN film-camera filter series).

### Verdict

**Strictly speaking, it hasn't "taken off" yet; it has only "started bringing in money."** Its rating count has stayed at 0 (appstore library 10-28 to 11-06, 0 every day). It reached the Japan Shopping top-grossing chart because **the bar for Japan's Shopping top-grossing chart is extremely low** : on the same chart, ranks 20–35 include 6 apps with 0–2 ratings (Gala-Gifts 1, Vereev 2, Grocery Tracker 0, Packager 0, WinStamp 2, Parcels Hub 1; appstore library 11-06). Its rank bounces between 18 and 72 (10-28 to 10-31 is 60→72,11-01, jumping to 21,11-02 to 18, then 25/35/43/27). This swing is typical of a few sales a day at the ¥980 level (inferred, not verified).

It sells a few more copies than many similar new apps from the same period, thanks to three things:

1. **Right category** : most similar apps sit under Business (6000) or Finance, but it is under Shopping (6024). On Japan's Business top-grossing chart, the established similar app Amacode ranks 37–85 and Seller Book 2 ranks 39–98. On the Shopping top-grossing chart, apart from the leader Seller Book (ranks 9–12), it is **the only similar app charting** . The same small revenue lands it in the top 30 in Shopping, where our recall picks it up.

2. **One-time ¥980 purchase, no subscription** : the main competitors are either subscriptions (Seller Book 2 from ¥980/mo, Furikan from ¥400/mo) or the old Seller Book one-time purchase (¥480 + ¥3,500). For side-hustle sellers who don't want another subscription, a ¥980 one-time purchase is a low bar and an easy decision.

3. **Store page copy that reads like a local wrote it** : the title "手数料・送料を引いた本当の利益を自動計算" (automatically calculates your true profit after fees and shipping), with the opening line "「売れた！」の次に来るのは、「で、いくら残った？」" (after "Sold!" comes "So how much did I actually keep?"), hitting the pain point of having sold something without knowing what you earned. No account, no server, no data collection, no full photo-library access, all listed as selling points.

### Growth data

- 2026-09-18 listed; version 1.0 → 1.0.1 (9-23) → 1.1.0 (10-06, "internal changes for future in-app events, replaced screenshots") → 1.1.1 (10-07, expanded to 33 languages). (App Store page)

- Japan Shopping top-grossing ranks: 10-28 60, 10-29 65, 10-30 68, 10-31 72, 11-01 21, 11-02 18, 11-03 25, 11-04 35, 11-05 43, 11-06 27 (appstore library chart_rank). Never charted on Top Free or the overall chart.

- Rating count: jp, 0,7 days, growth 0 (appstore library). No reviews to look at.

- The developer's other 2026 new apps from 9–October (MilliPrint, Prompter One, Lohnzeit, Nettorente, Tetrad) and the FilmN series have **never charted anywhere** in the library (no chart_rank entries). In other words, of the 6 localized tools this developer shipped in this round, only this one has started earning.

### Competitors

In the appstore library, there are 34 Japan-store apps whose names contain "フリマ / せどり / メルカリ / セラー" plus "利益 / 売上 / 管理 / 計算 / 帳". About 18 of them were newly listed in 2026 alone. This is a very crowded niche. The main players:

| Name | Platform | Launched | Scale | How it differs |
|---|---|---|---|---|
| フリマアプリの売上管理-セラーブック (Daisuke Yamashita) | iOS/Android | 2016-09 | 8,460 ratings, claims 250k downloads; Japan Shopping top-grossing ranks 9–12 | The leader, full-featured (product master data, multi-platform); old one-time purchase ¥480 + ¥3,500; the author is already steering users to a subscription model via Seller Book 2 |
| セラーブック2 | iOS/Android/Web | 2025-09 | 48 ratings; jp Business Top Grossing #39–98 | Subscription from ¥980/mo, screenshot bulk import, web version; listed under Business |
| かんたん利益計算 - せどりやフリマ | iOS | Not verified | 2,691 ratings; ranks 1 for "フリマ 利益" search | Just a calculator, no bookkeeping |
| Amacode(NAMBU SANGYO) | iOS | 2016-12 | 7,068 ratings; Business Top Grossing #37–85 | Research + sourcing + sales management for Amazon sellers (seller arbitrage), professional-oriented |
| フリカン(MAKASETE) | iOS/Android/Web | 2024-10 | 171 ratings; Business Top Grossing #132–186 | Subscription from ¥400/mo, web import, CSV import |
| Simple flea market income/expense memo | iOS | 2018-08 | 597 ratings; Business Top Grossing #122–163 | Long-running simple bookkeeping app |
| フリマネージャー(furimakaikei.com) | Web + LINE | Not verified | Not verified | Can automatically sync Mercari / Yahoo! Flea Market sales, and offers a free Google Sheets template; it does not have auto-sync |
| 2026 年新入局的个人开发者 App:せどり帳(07-28,13 评分)、うりログ(07-29,3)、フリマ売上管理(WEBDIA,09-07,3)、SellerNote(05-16,2)、物販会計 shiire(09-14,0)、かんたんせどり収支(08-05,0)、古物商の取引台帳(10-05,0)等 | iOS | 2026 | Ratings 0–15; none charted on the top-grossing chart except せどり帳, which hit the Finance chart once at #183 | Nearly identical features; the differences are mainly category (most listed under Business), pricing model, and copywriting |
| Google Sheets templates / tax-filing software (Taxnote, Yayoi, etc.) | Other | — | — | Alternatives; many sellers just use spreadsheets directly |

Bottom line: **no product-level exclusive advantage** . Compared with new entrants from the same period, it wins on category, one-time-purchase pricing, and store page quality.

### Growth tactics (where users come from)

- **商店搜索** :jp 商店搜"フリマ 利益"排第 19、"フリマ利益"第 20、"フリマ 売上管理"第 39、"フリマ 確定申告"第 9、"利益計算"和"メルカリ 売上管理"前 50 都没有(iTunes 搜索接口,11-06)。自然搜索位置一般,"確定申告"这个词是相对占优的。

- **Category chart exposure** : listed under Shopping, top-grossing ranks 20–40, which may bring some browsing on its own (inferred).

- **Apple Search Ads:** no direct evidence. The step-change in 11-01 rank from 72 to 21, plus the redesign and screenshot swap made specifically for "in-app events" 10-06, suggests some paid or promotional activity, but this is unverified.

- **Social / creators** : x-radar searches for "フリマ利益帳" and "Junmo Lee" returned 60 posts in the last 0 days; a TikTok search for "フリマ利益帳" found no related videos; Jina web search only turned up the store page, AppBrain, and auto-ranking sites like komori.tech / m-s-y.com. **No trace of any content channel.**

- **Multi-language** : expanded to 33 languages (10-07 before), but no store outside Japan has charted; Japan's default fee setup means nothing to foreign users, so this step looks more like a generic indie-dev copy-paste routine.

### Visibility

Barely known. No media coverage, no X discussion, no founder posting revenue; it only shows up on auto-scraping ranking sites (komori.tech, m-s-y.com Shopping top-grossing chart, "集計中 NEW").

### Copycats

No one has copied it specifically. If anything, it's one of the wave of similar new apps from 2026.

### Differentiation, and was it the reason it worked?

- On product: multi-platform fee presets (Mercari Shops and Yahoo! Flea Market both included), a one-tap "recently used" shipping amount, swipe to record a sale, a single-file tax CSV (UTF-8 BOM, opens directly in Excel), local storage with no account. Most similar apps have these too, so it counts as "well done," not as unique.

- On business: **the ¥980 one-time purchase** against the subscriptions most similar apps use is a genuine point of differentiation.

- On placement: **listed under Shopping** , so even a little revenue gets it charted and seen. That is the direct reason our recall picked it up.

- So: differentiation (one-time purchase + category + copy) does explain why it sells a few more copies than its new peers, but it is still far from "taking off." No ratings momentum, no content channel, no scale.

### Timing

Japanese individual sellers file their taxes (kakutei shinkoku) from 2 to March, so late year to early year is peak season for this kind of app (inferred). It launched in September with "CSV for tax filing" in its copy, timed to claim its spot ahead of peak. Whether it actually takes off depends on 2027 1 to March.

### What to borrow

1. In niche needs within a big market, **choose the category carefully** : the same tool listed under a category with a low top-grossing bar (Japan Shopping) gets charted and seen more easily than under the crowded Business category.

2. **Tools for subscription fatigue use one-time purchase** : a one-time ¥980 against competitors' monthly fees is an easy-to-explain selling point.

3. One developer spreading "local-need calculators" across many languages (Japanese seller profit, German night-shift bonus, German net pension…), mass-producing with AI and writing localized copy per country, is cheap to do; but this developer had only 1 of 6 tools earn anything, so the hit rate is low.

### Unknowns

- Actual revenue: can only be inferred from rank as roughly "a few sales a day"; there is no external data. The recall card's "developer's total monthly revenue about $3k, about 3k downloads/month" comes from a third-party estimation site, is unverified, and mostly refers to the FilmN series.

- Whether Apple Search Ads was used: unverified.

- Cause of the 11-01 rank jump: unverified (possibly ad spend, in-app events, or simply a few sales at the start of the month).

- Android version: not found.

### Sources

- appstore library (agent-im server DuckDB): chart_rank, app_day, app, app_name, app_snapshot, 2026-10-28 to 11-06.

- App Store page: [apps.apple.com/jp/app/id6811484795](https://apps.apple.com/jp/app/id6811484795) (version history, IAP ¥980, privacy "no data collected")

- Competitor IAPs: [apps.apple.com/jp/app/id1155107559](https://apps.apple.com/jp/app/id1155107559), id6745430211, id6736350775

- Developer page: [apps.apple.com/de/developer/junmo-lee/id1638994053](https://apps.apple.com/de/developer/junmo-lee/id1638994053)

- iTunes Search API(jp,2026-11-06)

- furimakaikei.com comparison article: [furimakaikei.com/blog/furima-uriagedkanri-app](https://furimakaikei.com/blog/furima-uriagedkanri-app) (2026-10-28 check)

- Privacy policy: [jlbizz.github.io/riekicho/privacy.html](https://jlbizz.github.io/riekicho/privacy.html)

- x-radar, TikHub TikTok search (no results)

This article was written by AI from public data and the data we collect daily. Numbers are sourced, and inferences are labeled.