suddenly crying is childish and immature, you must not have a good childhood, babe. Crying is to express feelings and crying actually works a lot of muscles, so crying is actually good for you not just for your mental and emotional state but for your physical state too.
It's not just a personality it's literally his feelings for Kihoon. You wouldn't cry for the person you care about?

why is the top such a crybaby?? its annoyingg. he acts all innocent then dominant the next. can the author pick a consistent personality the crying and shit is not effective or endearing at all, its giving childish and immature