The Isekai Returnee is Too OP for the Modern World

Morishita Taiju was transported into another world and became a hero, after wonderfully defeating the Demon Lord, he has returned to Japan. He was satisfied with his peaceful days as he hid his power, but... Hidden yokai and people with powers start to rampage, and the (rare nowadays) academy power battle-ish hidden world unfolds!! And now he trains beautiful warriors using superpowers!?