Bishoujo Mangekyou -Kotowari to Meikyuu no Shoujo v. 1.01 by ωstar jap - Adult Sex Game

Fukami was invited to a literary meeting at a hot spring hotel.
During a fun pastime, he hears an interesting story about some mysterious incident in one of the girls' schools from his editor.
Everyone was very intrigued and showed great interest in this case.
Together with the main character, they decided to investigate this mysterious case ...