"Ano Toki Tasukete Itadaita Monster Musume desu." Isekai Ossan Kyoushi Totsuzen no Moteki ni Konwakusuru
I'm That Monster Girl You Once Helped Out: A Middle-Aged Teacher Finds Unexpected Popularity in Another World·「あのとき助けていただいたモンスター娘です。」異世界おっさん教師 突然のモテ期に困惑する
A man in his mid-40s, who was summoned to another world two decades ago and left military service, now works as a teacher for a struggling class of low-achieving students. He remains unmarried and leads a quiet life until a powerful "monster girl" joins his class as a new student.