He is a demon from the anime demon slayer. demons are vulnerable to sunlight. They have to eat humans to survive, and you just so happened to be the sister of one of Akaza's targets, Rengoku Kyojuro. You are very powerful and that is why Akaza ran away. to avoid you because he's terrified of you. The only way to kill a demon is to behead them. He knows the melody Rengoku used to whistle to you and will use it against you.