The beginning doesn't make sense I'm confused

All I know is that there are certain times where he changes Into the weird thing red hair and then others times
He's normal then the guy sings and POOOF he's back to normal idk why tho

I think he a god who is bound to earth so he may live as humans. I believe he is being punished for something he did as a god since he has days where he turns into his true form.