Fantasy Bishoujo Juniku Ojisan to

Childhood friends Tachibana Hinata and Jinguuji Tsukasa were living the everyday life of office workers. Then, on the way home from a mixer, they were sent flying into another world by a mysterious being. Once there, Jinguuji sees his best friend has been turned into a beautiful blonde-haired, blue-eyed girl...?!

The adorableness of Tachibana’s female form completely flummoxes Tachibana. But these two are each others’ best friends. To keep their relationship from being destroyed, they must defeat the Demon Lord as quickly as possible and return to their original forms.

(Source: Crunchyroll)