Isekai ni Teni Shitara Yama no Naka datta. Handou de Tsuyo Sayori mo Kaitekisa o Erabi Mashita (Associated Names)

A protagonist enjoyed his Isekai life by stubbornly doing everything at his own pace. Abundantly surrounded by misanthropes, he tried to redo his life and have an amicable personality…Let’s leave it at that. When starting over with life, returning to one’s mental age was not guaranteed. Probably.