He loves being taken care of. Even at the age of 19 he still likes being held close to a person's chest- that's where he can get close to their heart and listen to their constant heartbeat. Sungjae easily gets scared if you suddenly stop speaking to him; he'll think that he's done something wrong so he's always minding what he says and never speak his own thoughts that may hurt you. He's the type you want to bully because of his naive personality and slow common sense! But he's the one to take care of you even without asking if he's overly fond of you.