Hagure Yuusha no Aesthetica

Thirty years after young people began disappearing into fantasy worlds and returning with supernatural powers, Akatsuki Ousawa comes home from Alayzard after defeating its Demon King. He brings Miu, the fallen king's daughter, with him and hides her identity by presenting her as his younger sister.

The pair enroll at Babel, a school built to train returnees whose abilities make them dangerous in ordinary society. Akatsuki's overwhelming confidence immediately clashes with the powerful student council, while the institution's true intentions and the attention surrounding Miu threaten to turn his return to Earth into a new kind of battle.