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Full Financials of the Tech Doujinshi "Riakuto!" at Techbook Fest 5 — ¥730K in Sales, ¥270K in Costs, ¥460K Take-Home

Yuka Ooka, who sold the React primer "Riakuto!" at Techbook Fest 5 (Gijutsu Shoten 5), publishes her full accounts: total sales of ¥731,262 (¥435K cash + ¥150K deferred payment + ¥137K BOOTH, etc.), expenses of ¥271,807 (¥228K printing, etc.), and gross profit of ¥459,455. Two volumes, roughly 600 copies. A definitive real-data example of self-published technical books as "event-driven content sales."

This is a translation of the Japanese original. The Japanese version and cited primary sources are authoritative for all figures.

The published numbers

ItemFigure
Total sales¥731,262
└ BreakdownCash ¥434,600 / Kantan Atobarai (deferred payment) ¥150,500 / pixiv PAY ¥9,000 / BOOTH (8 days after the event) ¥137,162
Total expenses¥271,807 (¥228,000 for printing 400 copies × 2 volumes, ¥7,000 participation fee, etc.)
Gross profit¥459,455
Copies sold~600 (both volumes combined; print ¥1,000 each / download edition ¥1,500 / set ¥2,000)
Title“Riakuto! Painless React Development with TypeScript”

Breaking down ¥460K from a single-day event

Techbook Fest (Gijutsu Shoten) happens once or twice a year, for one day. This “time density of revenue” contrasts sharply with Kindle publishing, which stacks tens of thousands of yen per month as stock income — with self-published technical books, half a year’s revenue concentrates on event day. Note the ¥137K from BOOTH: 19% of total sales was added through digital copies in the 8 days after the event ended. The event is a “sales day,” but it is simultaneously a “promotion day” when social media exposure peaks — and capturing that heat through digital distribution afterward has become the standard two-stage play.

The dominant expense is printing (¥228K), which is inventory risk incarnate. Misjudge the print run and gross profit evaporates fast. Techbook Fest offers a pre-event demand signal — the “check count” (how many attendees have bookmarked your booth) — and setting the print run based on it is standard practice. Doujinshi are “publishing with advance demand measurement” — the decisive difference from ordinary self-publishing.

Why the topic choice was inevitable

“Riakuto!” targeted React × TypeScript — a domain professionals needed immediately at work, yet one where no definitive book existed at the time. The conditions for a tech doujinshi topic that can sell hundreds of copies are: (1) practitioners are struggling with it, (2) commercial publishing hasn’t caught up yet, and (3) the author uses it heavily in their own work. This stands on the same demand base as the technical-article economy that underpinned Zenn’s acquisition by Classmethod. The contrasting example cited as the second source — a GitHub Actions book (~500 copies) — satisfies exactly the same conditions.

It’s also worth noting that “Riakuto!” went on to become a long-running series through repeated revisions. A doujinshi need not be a one-time festival: it can become a “versioned stock asset” that sells again with every revision.

Sources

This article summarizes and analyzes the public sources above. Please refer to the primary sources for details.