Contained a virus that my anti-virus luckily stopped!
There's this thing. Called a signature. Software makers sign files they release. What bad anti-virus programs do to detect viruses is that instead of actually searching for harmful files, they just search for a signature. Bad anti-viruses do this because they're cheapo scams that would rather slap band-aids on things than develop actual problem-solving code. If there is no signature, they flag it as a virus unconditionally.
The only people who sign shit are corporations like Microsoft or Valve. So, of course something like this that's basically made by an indie is not going to be signaturing it's files.
And by a Japanese indie, no less. The Japanese are fuck awful at computer platform software. It's why so many tiny VNs will peak your CPU despite not doing anything intensive. They don't know how to code or optimize for the platform at all. Let alone how to signature something. There are Steam ports of Japanese games with such fucked ports, they'll set off anti-viruses this way as well because they were ported by Japanese coders.
The game is fine. Your anti-virus is just bad.
EDIT: Typo.