So far Yunho seems to be the only sane person in this webtoon.
Naru is just plain frustrating. I understand he had a trauma but he is not the only one in this world. Everyone has their own troubles and worries. He's so touchy-feely about his own condition but uber insensitive towards other people. Come on, he is 25 years old but his mind set is of a kid. Why does he even need a girlfriend at this point? I doubt he even sees Sumi in any sexual context.