About
I'm a frontend engineer in Tokyo. I run Zenkaku on my own, and I wrote a book on frontend testing.
I've built web products at several companies in Japan. I then joined a major video streaming service in Japan as the first engineer of its in-house frontend team, and I've been moving its web development in-house since. I work on the web and connected-TV apps, and I spend a lot of my time on tests and test strategy.
Zenkaku is my own project. It isn't connected to my employer.
Japanese text goes through an input method: you type the reading, pick the kanji, and press Enter to confirm it. Apps built by teams that don't type Japanese often treat that Enter as "send". When I went through public bug reports, I found 85 about Japanese input or display, filed against 64 products. Most were this kind of bug.
So I check products by hand, the way someone in Tokyo would use them, and send a short report with screen recordings and the fix.
基本からしっかり学ぶフロントエンドテスト入門. A 328-page book in Japanese, from static checks and unit tests to component, E2E and visual regression tests, test strategy, and testing with AI. Published by Gijutsu-Hyoron in June 2026. Publisher page · Sample code
How we moved web frontend development in-house without slowing releases: a design system, API types generated from OpenAPI, and tests. In Japanese, with a co-speaker.
Slides in Japanese. Speaker Deck
Slides in Japanese. Speaker Deck