I Built a Manga Release Reminder App Just for Myself

Everyone has a free app or two on their phone that “costs nothing but turns out to be full of little annoyances once you actually use it.” Not long ago, the only options when something annoyed you were to put up with it or go hunting for another app, but lately the bar for thinking “wouldn’t it just be easier to build this myself?” has dropped quite a bit.

This time, a free app related to new manga volume releases was annoying me, so I decided to build my own.

I only wanted two notifications.

One week before a new volume of a manga I follow comes out: “time to preorder,” once. And on the release date itself: “it’s today,” once more. I preorder on my own online, so a week’s notice is enough, and the day-of notification serves almost no practical purpose; it exists purely to make me happy while I wait for the book to arrive. I wanted something that looks up the release date, remembers it per title, and taps me on the shoulder exactly those two times.

What came out of that is an Android app called MangaGo, used only by me, distributed to no one. I built it the way I usually do these days: I wrote a spec in Markdown, handed it to Claude Code, and left almost all of the implementation to it. I started on the night of September 29, and it was basically working by the morning of October 1 — a weeknight idea running on my own phone two days later.

Registration works with either the title or the author’s name. There’s just one input field, and even if you type something approximate from memory, it pulls up a mixed list of likely titles and authors.

This turned out to be quite capable. During development, when Claude Code was operating the actual device to check behavior, it couldn’t send Japanese text through adb, so it typed “frieren” in romaji, and the keyboard’s conversion turned it into “ｆりえれｎ” in the field. Even a human would struggle to read that. Even so, Frieren: Beyond Journey’s End came up as the top candidate, correctly, with both the original author and the artist listed.

That got a laugh out of me.

Frieren still ranks first even with “ｆりえれｎ.” Titles and authors come up mixed together

Registered titles appear in a list, showing the upcoming volume and release date at a glance. The calendar screen shows release schedules for the next 30 days, with a dot marking each release date. The bell icon on the right shows whether the 7-day-before notification has already gone out; for Kimi wa Yotsuba no Clover, the reminder already arrived the other day.

List of registered titles

Release schedule for the next 30 days. A lit bell means the 7-day-before notification has already been sent

So how does it look up release dates?

The app calls the Claude API itself and has it run a web search to find out. No server runs anywhere — it’s built to work entirely on the phone. The model is Claude Haiku 4.5, and each lookup costs roughly $0.06. Before building it, I compared it against Sonnet, and I was a bit surprised that the cheaper Haiku actually performed better. That part of the tuning was interesting enough that I’ll write it up in a separate post.

At $0.06 per lookup, the monthly cost depends on how often the app checks. So I added frequency presets in the settings screen, and selecting one shows the estimated monthly cost in dollars. With my current registrations (9 titles, 2 authors) at the standard frequency, it comes out to roughly $2.60 a month. For titles without a confirmed release date yet, it checks once a week; once a release is close, it checks again to make sure there’s been no delay. It only goes looking when it actually needs to.

Selecting a check frequency shows the estimated monthly cost in dollars

The total API cost from all the testing during development came to about $20.

I had Claude Code make the icon too. I only asked for “something that deforms a four-panel manga layout, just go with it,” and it stacked four panels vertically with a ”!” in the last one. The first draft just looked like four horizontal bars stacked up, and the ”!” was so small it read as a dot, so I had it narrow the panels and enlarge the ”!”. I was a little impressed that it checked the coordinates to make sure the corners wouldn’t get clipped when cropped into a circle.

Four panels stacked vertically, with a ”!” in the last one

At 8 a.m. on October 7, two real notifications are scheduled to arrive. One is the release-day notice for volume 11 of Kimi wa Yotsuba no Clover; the other is the 7-day-before reminder for volume 16 of Sonna Kazoku nara Sutechaeba?. The former is exactly the kind of notification that exists purely to make me happy.

Building an app for nobody but myself means I don’t have to worry about anyone else.

At this rate I’ve started steadily replacing the apps on my phone with ones I built myself.

The classic 2000s freemium route of “ad revenue from a free app” may be getting swallowed up by a game-changer nobody back then could have imagined.

This piece was written with concept and direction by Yuichiro Kuzuryu, text by AI.

Originally published in Japanese at https://clazytech.com/2026/10/1861/. Translated with LLM assistance and reviewed before publication.