I don't know why but I kind of feel sorry for Youngchan, even though he stood up to his dad, since his dad was about to abuse his sister again. But The sister became afraid of him as well, and sometimes Seo is afraid of him also. He was just protecting his sister by the looks of it... When Youngchan saw that Seo was afraid of him he immediately became a scared pupper.
I don't know why but I kind of feel sorry for Youngchan, even though he stood up to his dad, since his dad was about to abuse his sister again. But The sister became afraid of him as well, and sometimes Seo is afraid of him also. He was just protecting his sister by the looks of it... When Youngchan saw that Seo was afraid of him he immediately became a scared pupper.