Honestly that's not even psychopathic that was self defense + protecting his brother
It was justifiable because they were horrible people but doing that with a big grin on your face is pretty nuts
I don't think he was psycho for what he did to his dad ngl. But the way he acts with the mc is def psycho behavior. Still love him though. He's a little sick and twisted but his family is all rather sick in the head (except the mom, can't believe she got murdered just for being concerned for her babies)
I don't think what he did wasn't justified, I mean his dad was awful, but the way he carried it out was pretty psychotic. I imagine most kids in a situation where they feel no way out but to kill their parents which I'm sure is very few anyway wouldn't do it without batting an eye but he was either happy or completely nonchalant
I love my precious psycopath Shirayuki.