Jingai Kyoushitsu no Ningengirai Kyoushi

Rei Hitoma is a former schoolteacher and a self-professed misanthrope due to past trauma. Hoping to live a slow, relaxing life, he takes a new teaching job in the mountains. But it turns out that this place is actually an all-girls school for demi-humans who want to become full-fledged human beings!
(Source: Yen Press)