I think I finally managed to find the game!
It's called Koumon No Hana by Studio Bakanal
https://vndb.org/v25090
It's no longer on itch io,
but the devs have an email and twitter, so maybe you can ask them for a copy of the game?
https://studio-bakanal.itch.io/