DmonMaster
A grind-free 3v3 auto-battle hack-and-slash about collecting 100 Dmon; the solo developer says AI has written all of the code since January 2026, on top of a core written by hand in 2025.
Links go to the official store or developer page. Last verified Nov 4, 2026.
Where to play
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- View on SteamSteamReleased$8.88
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Desktop · Steam
About DmonMaster
DmonMaster is a single-player 3v3 auto-battler for Windows that its developer calls a grind-free hack-and-slash. You are summoned to the world of DREAL, home to 100 beings called Dmon, and set out to gather them all. You choose a team of Dmon and they fight each battle on their own; each Dmon has its own abilities, and the game is about working out which combinations make a strong deck. Battles drop Dvice, equipment for your Dmon, some of them rare. There is no experience and there are no skill points, so every Dmon is ready to fight as soon as you have it. DREAL is divided into Domains, each ruled by a Dmon, and beating a Domain's battle adds its ruler to your team. The developer, Harusame, describes the cast as girl characters and says the point of hack-and-slash for them is building, not action or button pressing. They say they wrote a core of a few tens of thousands of lines by hand in 2025 and have not written a single line of code in 2026: AI now writes the code, documents, Issues and commits and operates the Unity Editor, in up to six sessions at once, while the developer decides direction and structure and approves. The Steam AI disclosure lists general coding, general imagery including character art and skill icons, all background music, some sound effects and general translation. US$8.88 on Steam since 3 Aug 2026, with a free demo, in 13 languages.
Screenshots and art
DmonMaster key art · Steam store artwork
How it was built
Partially verifiedThe developer's Zenn article says they code only with AI, write no code themselves and do not even read it: code, documents, Issues, commits and Unity Editor operations are all done by AI, with up to six sessions running at once, while the developer sets direction and structure and approves. They wrote the core of about 20,000 to 30,000 lines largely by hand when full development began around July 2025, and have not written a line since the start of 2026. As of 23 Sep 2026 the single repository held 721,327 lines in 7,361 files (632,566 lines of code, 44.5% of it tests), and 5,211 of its 5,722 commits dated from 2026. About 140,000 lines are infrastructure that lets the AI work on its own, all written by the AI: Toko, an in-house MCP server for driving the Unity Editor; harutools, which runs hooks and checks; and the Xyzson hub. The article is tagged Claude Code and explains why the developer does not use Claude Code's Skills and auto-memory features, replacing them with their own index of rule documents, but it does not name the tool or model that writes the game's code.
- DeveloperSteam AI disclosure: “General coding. General imagery, including character art and skill icons. All BGM. Some sound effects. General translation.” — Steam
- DeveloperLaunch post on note (5 Sep 2026): apart from the first core code, the developer has written no code in 2026; the codebase then stood at 620,360 lines, and character and equipment images, music and translation were also done with AI. — note (はるさめ)
A Unity game in C# built by AI agents under a self-made control system. Game specifications, including all 100 Dmon and 200 Dvice, are written in Markdown, and the AI implements changes to them; the interface uses UI Toolkit and USS so that visual changes are text diffs. Instead of Claude Code's Skills and auto memory, the developer uses an index of about 600 rule documents (“abilities”) that hooks force the AI to read before touching matching files, 181 banned code patterns, checks at four stages (before and after edits, at commit and at release), an in-house MCP server (Toko, 51 Unity tools) that compiles, tests, builds, runs long soak tests and records store screenshots and trailers, and a release gate of six fixed phases. Each of up to six parallel sessions works in its own copy of the repository with its own Unity Editor; development is trunk-based without pull requests.
- Engine / framework
- Unity
- Languages
- C#
- Team size
- 1 (solo)Developer Reportednote (はるさめ)
- Development time
- Not disclosed
- Development cost
- Not disclosed
- AI-written code
- Not disclosed
“基本的に、コードも文書もIssueもコミットも、Unity Editorの操作も、AIがやっています。”Verification notes: AI use comes from the developer's Zenn article (23 Sep 2026, Japan time), which links the Steam page and both note posts, the launch post on note (5 Sep 2026) and the developer-written AI disclosure on the Steam page (re-read on 4 Nov 2026). The Zenn figures are taken, the article says, from the repository as of 23 Sep 2026 and include development infrastructure, not only game code; the note post's 620,360 lines are an earlier count. The developer says the 2025 core was written largely by hand and has since been heavily reworked, so no AI code share is recorded. The tool is undisclosed: the article is tagged Claude Code and discusses Claude Code features the developer does not use, but never says which tool or model writes the code. The developer also says the article's details were based on a summary written by AI. Release date, price, platform, the 13 languages and the demo (released 27 Aug 2026, playable up to level 33 with saves carrying over) come from the Steam store API; the review figures from the store page on 4 Nov 2026. Team size: the note post calls the developer an individual developer (個人開発者). A second note post (18 Sep 2026) explains the design: the developer, a fan of Diablo-style hack-and-slash games, wanted building without action or button-pressing; those games are named as background only, and no names or assets from them were found. Location is not stated.
Development history
- June–July 2025
First commit (June 2025); full development starts around July 2025, with the developer writing the core code largely by hand.
DeveloperZenn (はるさめ / tokoharusame) - January 2026
From the start of 2026 the developer writes no code; the AI writes it all. Monthly commits rise from 73 in January to 864 in July.
DeveloperZenn (はるさめ / tokoharusame) Released on Steam for Windows.
OfficialSteamA free demo, playable up to level 33, is released on Steam.
OfficialSteamThe developer describes the AI-only development setup on Zenn: 721,327 lines in one repository, 5,211 of 5,722 commits made in 2026.
DeveloperZenn (はるさめ / tokoharusame)
Game performance
Each figure measures something different — concurrent players, owners, downloads and sales are never interchangeable and are never added together. Labels show where each number comes from.
Steam
US$8.88 on the Steam store API (US region) on 4 Nov 2026. Windows only. A free demo (playable up to level 33, with saves carrying over to the full game) has been on Steam since 27 Aug 2026.
All reviews as shown on the store page on 4 Nov 2026 (rated Mixed).
Share of positive reviews among the 22 shown on the store page on 4 Nov 2026.
Not publicly available: Concurrent players, Estimated owners, Copies sold, Gross revenue.
Reviews & rankings
Not yet reviewed by our editors.
Sources
| Source | Type | Published | Accessed |
|---|---|---|---|
| コードを1行も書かずに72万行のゲームをAIに作らせている開発環境解説 Zenn (はるさめ / tokoharusame) · Japanese | Devlog | Sep 23, 2026 | Nov 3, 2026 |
| AIに62万行書かせたゲームを発売しました。 note (はるさめ) · Japanese | Devlog | Sep 5, 2026 | Nov 3, 2026 |
| ハクスラが好きすぎたのでハクスラゲームをAIで作ってSteamで発売した件について。 note (はるさめ) · Japanese | Devlog | Sep 18, 2026 | Nov 3, 2026 |
| DmonMaster on Steam (store page incl. AI Generated Content Disclosure) Steam | Store page | Not confirmed | Nov 3, 2026 |
| DmonMaster Demo on Steam (store API entry) Steam | Store page | Not confirmed | Nov 3, 2026 |
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