Yuusha in Maou n Chi

Synopsis

To an immortal, all-powerful Demon Lord like Wisped, fending off heroes is a daily occurence. However, as he was not born to be in battle, Wisped's heart was filled with nothing but loneliness, until one day when he met with a hero named True. Thinking that the guffawing, unarmed man had come to defeat him, the boy instead asked him an absurd question... "Could I live in your castle?" (Source: Kuma)