Itoshii Akuma: Shitto

Despite his best efforts, Akiyoshi Tooru has fallen for the very beautiful but sadistic and perverted demon, Naruse Fuuta. Not only do they attend the same university, they're now living together! Though Akiyoshi has always tried to be careful about their night life, he never expected Naruse to stop touching him altogether, and then all of a sudden, Naruse is in an accident and reverts to his adolescent self!