A Hero in the Demon's Castle

A grumpy immortal Demon Lord reluctantly becomes roommates with a golden retriever type Hero.

To an immortal, all-powerful Demon Lord like Wisped, fending off heroes is a daily occurrence. 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?"