Isekai Hoikuen wo Hirakimashita: Fusei Skill de Saikyou Loli Seirei-tachi wa Deredere desu

Oliver, an adventurer almost in his forties, received a certain mission due to his earnest personality. That mission is to bind a contract with deredere little spirits who have great power?! Thus, the spirits gathered and the new life of Oliver as school principal began!!

(Source: Overlap, translated)