I Got a Cheat Skill in Another World and Became Unrivaled in the Real World, Too, Vol. 5 (Light Novel): Volume 5

Yuuya Tenjou successfully repelled the attack by Yuti, a girl who transformed into a devil. With her defeat, the tragic truth behind her anger and dark emotions was revealed. Moved by her plight, Yuuya takes mercy on her...and now they're living together?! He thinks he might be able to help Yuti by using his own body to seal the demonic power that has taken root inside of her. Will the unrivaled young man from another world transform into an unrivaled, sinister devil?!