Mashumaro Trigger!
A free slice-of-life comedy visual novel about a squishy-cheeked first-grader and the big sister who adores her.
Links go to the official store or developer page. Last verified Nov 3, 2026.
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Desktop · Steam
About Mashumaro Trigger!
Mashumaro Trigger! (Japanese title ましゅまろトリガー！) is a free slice-of-life comedy visual novel about two sisters. Mashiro is a curious, guileless first-grader whose soft, squishy cheeks have earned her the neighbourhood nickname "Mashumaro-chan" (Mashiro plus marshmallow); her big sister Mio, a capable cook who dotes on her, looks after her while their parents are overseas. The story follows the everyday chaos of the two with their friends, neighbours and family. The store page lists a main story of more than 160,000 words, roughly 10 to 15 hours long, with chapter select, an opening movie and an ending sequence with theme songs, a music room with 13 tracks, a gallery of 19 event CGs, nine bonus scenarios, and auto, skip, backlog and 12 save slots. It says the game is free, with no in-app purchases and no paid content. The developer's Steam AI disclosure says Claude Code implemented the game (engine and game code), was used with OpenAI for the extra scenarios and for the English translation of the main story and extras, and that the graphics were made with OpenAI and the music and sound effects with Suno; all of it was generated during development, and nothing is generated at runtime. Free on Steam for Windows since 3 Sep 2026, in Japanese and English.
Screenshots and art
Mashumaro Trigger! key art · Steam store artwork
How it was built
Partially verifiedThe developer's Steam AI disclosure lists generative AI by content type. Game implementation (engine and game code): Claude Code. Extra scenarios, concept and writing: OpenAI and Claude Code. English text (translation of the main story and the extras): Claude Code and OpenAI. Graphics (character art, backgrounds, event CGs and store images): OpenAI. Music and sound effects (two theme songs, background music and effects): Suno. It says all of this was generated during development and shipped with the game, and that nothing is generated at runtime. The store text adds that part of the extra scenarios was made with generative AI and that details are in the in-game credits. No OpenAI product or model is named, and the disclosure does not say who wrote the main story.
Per the Steam disclosure, Claude Code built the game's engine and game code; OpenAI and Claude Code worked on the extra scenarios and the English translation, OpenAI made the graphics and Suno the music and sound effects, all before release. The store page's legal line says the game was made with Unity; no workflow is described beyond that. Version 1.1 (6 Sep 2026) added keyboard navigation of choices, a right-click menu and some replaced background art.
- Engine / framework
- Unity
- Languages
- Not disclosed
- Team size
- Not disclosed
- Development time
- Not disclosed
- Development cost
- Not disclosed
- AI-written code
- Not disclosed
“Game implementation (engine, game code): Claude Code”Verification notes: The AI claim rests on the developer-written AI disclosure on the game's Steam page (re-read on 4 Nov 2026), which names Claude Code for the game implementation (engine and game code) and lists OpenAI and Suno for the art and music; no share is given. The Japanese title ましゅまろトリガー！ is the name shown by the Steam store API in Japanese. Release date, free price, Windows-only and languages (English and Japanese) from the Steam store API on 4 Nov 2026; the review count from the store page the same day. Version 1.1 from the developer's Steam news post of 6 Sep 2026. Steam lists no website, and no other source about the game or its maker was found. The store page's legal line reads "© 2026 夢喰い鯨 / PLK Studio" and "Made with Unity."; it does not say who or what 夢喰い鯨 is. The disclosure says nothing is generated at runtime. Steam shows no mature-content descriptors; the store page describes a family-friendly comedy.
Development history
Released free on Steam for Windows, in Japanese and English.
OfficialSteamVersion 1.1 adds arrow-key navigation of choices and menus, a right-click menu during scenes and some replaced background art, and fixes save issues.
OfficialSteam (Mashumaro Trigger! news)
Game performance
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Steam
Free on the Steam store API on 4 Nov 2026; the store page says there are no in-app purchases and no paid content. Windows only.
All reviews as shown on the store page on 4 Nov 2026; Steam shows no score until a game has 10 reviews.
Not publicly available: Concurrent players, Positive Steam reviews, Estimated owners, Copies sold, Gross revenue.
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Sources
| Source | Type | Published | Accessed |
|---|---|---|---|
| Mashumaro Trigger! on Steam (store page incl. AI Generated Content Disclosure) Steam | Store page | Not confirmed | Nov 3, 2026 |
| Update v1.1 is now live Steam (Mashumaro Trigger! news) | Devlog | Sep 6, 2026 | Nov 3, 2026 |
