Bringing Claude Code from the Mac to the iPhone: a veteran Japanese developer's ¥2,000 tool hit #21 in the Japan Business Top Grossing chart within three days of launch

Casement, listed on the App Store on Oct 29, does something old: it remote-controls your Mac at home. The difference is that it doesn't shrink the entire screen onto your phone. It takes Mac apps one window at a time, and each window behaves like its own app on the iPhone, iPad, or Vision Pro. With only 14 ratings, it reached #21 in the Japan App Store Business Top Grossing chart on Nov 1, ahead of Jump Desktop, which has been around for over a decade. Below: how it got going, where the money comes from, who's competing, and whether the step the author says he doesn't know how to take is an opening for you.

Nov 2 evening: the author says "I have no idea how to push it out"

On the evening of Nov 2 (Japan time), Casement's author MIRO (@MobileHackerz) posted on X:

My app "Casement" is already known to most of the people in my own follower circle (probably the digital enthusiast crowd?). I have no idea how to reach the so-called Apple fan community or overseas audiences. I think that once it reaches people, someone will like it.

This post got 22k views. That day, Casement ranked #22 in the Japan Business Top Grossing chart, after its previous best of #21. Then it kept sliding: #11-03, #38,11-04, #48,11-06, #51 (App Store Japan, Business Top Grossing).

The author laid out the problem himself: the first wave of users came from him. Once that wave passed, he doesn't know where the next one will come from.

What it is

In one line: not remote desktop, but "remote apps". The first paragraph of the store listing says: "This is not a remote desktop that mirrors a shrunken screen. Casement opens each window of your desktop apps one by one, as apps on the device in your hand. Spreadsheets, editors, and AI agents running on your computer can keep going even when you step away."

What you can do with it:

• Tap an app in the Dock to open a specific Mac app, with the menu bar still working as usual;
• On iPad, each window is a separate app that can be split-screened side by side; on iPhone and iPad, you can open a Mac app directly from home screen widgets, long-press icons, or Spotlight; on Vision Pro, windows can be placed freely in space;
• Type Japanese with the iPhone's own keyboard (flick input, predictive conversion), with an extra row above the keyboard for Esc, Tab, Command, and arrow keys;
• If the Mac is locked, you can enter the password on your phone to unlock it; sound plays through the phone;
• The device connects peer-to-peer to the Mac, with no account and no relay server; for use outside your network, you need to set up Tailscale yourself.

The requirement is also stated on the store listing: only Apple Silicon Macs running macOS 26 or later are supported. Free to download with a 7-day trial, then a one-time in-app purchase of ¥2,000.

Why now, and why him

1. The author is the channel. MIRO's real name is Iwaki Shinnosuke. He wrote the "携帯動画変換君" that everyone among Japanese phone users used for 2004 years, and he designed VRM, the 3D avatar format. He is currently CTO of Virtual Cast. His previous project POPOPO shut down in September of 2026, and Casement was released right after as a personal project. The launch tweet from October 30, "It took a while, but I've released Casement, which brings Mac apps remotely to your iPhone / Vision Pro", got 253k views, 1.5K likes and 1.2K bookmarks (X, read on 11-06). Bookmarks almost matching likes means many people are "saving it to install later". The tech journalist Munechika Nishida posted the next day: "Using it since yesterday, it feels excellent".

2. Timing. Apple's foldable iPhone Duo launches in October, and remote desktop apps are piling in: Sill 10-08 went live, Screens 10-11 added iPhone Duo support, and Astropad Workbench 10-27 shipped a 1.4 version. On launch day, Japanese Apple media AAPL Ch. wrote up Casement, saying remote desktop apps are "back in the spotlight."

3. People who want to watch AI work from their phones. One five-star review describes the user profile very accurately:

I don't want to remote the whole screen, I just want to remote a few apps (I use Claude Code and Codex)! This app is exactly for people like me. Subtractive thinking that cuts away the extras and makes the experience better. If your use case matches, you'll find it unique. The one-time purchase is also appreciated. (App Store Japan, 10-31)

Another X user, 11-03, wrote that they used Casement to operate the Mac version of Codex from an iPad with a Magic Keyboard while out, saying "I'm finally free of the hassle from before." They also said that for apps like VS Code or Xcode, which don't have iPad versions, being able to use them on an iPad is very appealing.

4. Details built for Japanese users, plus a one-time price. Another five-star review: "Made in Japan, and the Japanese input is perfect. There are similar apps, but I think this is the best. The one-time purchase is also appreciated." Compare prices: Screens is a monthly subscription, Astropad Workbench is $14.99 a month, and Jump Desktop sells for ¥2,500 as a paid download in Japan. A ¥2,000 one-time purchase with a 7-day trial turned the author's fans' curiosity into payments quickly.

No sign of ad spend, influencer deals, or chart-pushing turned up. The traffic came from the author's X posts, two articles from AAPL Ch., and word of mouth from users.

How the numbers moved

(App Store 日本区,10-31 至 11-06;平均 4.36 分。香港区商务畅销榜 11-01 进过第 75,之后掉出;美国区 0 个评分。)

A few takeaways:

• The Japan business chart's bar is low, and many of the top 50 are small tools like PDF scanners and voice recorders. 14 ratings roughly map to a few hundred to a thousand-odd downloads (estimate). At ¥2,000 per sale, first-week revenue lands somewhere around ¥0.3M to ¥2M (estimate, unverified).
• This is a launch spike, not sustained growth. From the 1.0.4 update (adding Apple Pencil support and biometric unlock) on 11-05 to 11-06, it still hasn't pushed the ranking back up.
• Negative reviews focus on connectivity: VPN connections using SSTP fail, and with Tailscale it sometimes reconnects endlessly. Some users also want the trackpad and keyboard to be shown at the same time.

Who it's competing with

So "remote by window" isn't unique to Casement, and the free open-source Sill came first. Casement wins in Japan on Japanese support, the author's reputation, and the one-time price. With the same features, Sill has only 3 ratings on the Japan store.

How many people know about it now

A small circle. Japanese Mac and dev folks learned about it through the author's X account and AAPL Ch.; it has 14 Hatena Bookmark saves and never made the hot list; there's no English coverage and no US-store ratings. The author himself says he hasn't reached the Apple fan community or overseas yet. I found no products copying it; similar tools are each moving in this direction on their own at the same time.

If it were you

C: worth learning from, but not a good bet to follow. It took off on the author's twenty years of reputation and Japanese localization, and you can't get either. The core "remote by window" feature already has Sill, which is open source and free; full-screen remote has a lot of established products; and "watch your AI agent from your phone" is being built by Anthropic and Astropad. The user base is also narrow: people on macOS 26 with Apple Silicon, who keep a Mac running and are willing to set up Tailscale.

Good fit for: Mac / iOS devs who already have followers in a language community, have the technical skills for low-latency streaming, and want to build a small tool that sells as a one-time purchase.

Not a good fit for: people with no audience of their own, and people who want this to become a lasting business. Its curve is a single spike: it dropped from 21 to 51 within a week.

How to do it: two realistic paths. ① Do a "Casement for another language": build on Sill's open-source code (Apache 2.0 allows commercial use; keep the attribution), focus on languages with complex input methods like Chinese and Korean, get the input experience right, and set a one-time price. ② Build for a platform it skips: Casement and Sill are both Mac-only. As far as I can tell (inference, not fully verified), there's no solid consumer product yet for remoting a Windows window to your phone.

How to get users: copy its approach. Post a demo video that explains "not remote desktop, remote apps" on your own X or in the relevant language community, then pitch a local Apple outlet for a write-up. In the AI coding crowd, "keep running Claude Code / Codex on your iPad while you're out" lands much better than talking about remote desktop.

Window to act: the attention around iPhone Duo and "watch your AI agent on your phone" is happening in these few months. Once Anthropic or OpenAI finish their own mobile remote features, the users who only want to remote Claude Code / Codex won't need this kind of tool.

What would show I'm wrong: ① if Casement's ranking recovers after 1.0.4 and holds in the top 50 of the Japan-store Top Grossing chart for a month or two, a one-time-purchase small tool can earn ongoing revenue, and the grade should go up; ② if Sill or someone else quickly adds Japanese and Chinese input, the language-localization gap won't hold, and following it is even less worth it.