What he did to byul is what his parents did to him. :(

I think that's the best he could do right now,... He's vulnerable and exhausted mentally,, some parents prefer it hide the pain because it may cause more damage to their kids if they do interact with them... Everyone needs an alone time.. especially the mental damage he took with what his father told him, it's best for him not to be near byul, since kids that age arw sensitive to negative emotions