I am Enmu (Human), I like to fool people and make others feel annoyed with me.

FIRST PART - Enmu likes to trouble people and also deceive anyone he meets.

SECOND PART - Enmu finds someone good and changes himself for the better, whether it's building a relationship or otherwise.

THIRD PART - Eventually Enmu changed and became better, his life course changed and he didn't become a demon, he didn't even meet Muzan.

The background story is around the 1810s, the Edo period.