The Ragnarok System of the Desperate Reincarnated Demon Lord and the Seven Aggressive Maidens, Vol. 1 (manga)

Rintarou, a renowned hero who helped save Japan from being taken over by demons, has become an unconfident university student. Though he still has his incredible abilities, there’s one thing he doesn’t have—a girlfriend. But one day, a princess suddenly approaches him and asks to be his wife, his girlfriend…or even his friend with benefits!?