The Demon Lord and his Hero (BL)

[When Demon Lord, Syryn Nigh'hart, found that he had gone back in time and turned into his child self, he had assumed to do better with his second life - commit smaller crimes, keep away from burning villages and inciting other demons, contribute to society, abide by most laws, you know? But then the hero, his old friend, had to fall in love with him and ruin his plans., \