he is friendly and humble, not think twice to help someone who needs it. he is mature outside but clingy inside. he is so kind and comes from a rich family. he also smart because he's a student of a too university. with his girlfriend, he easily got jealous and sulky. when he's angry, he slightly has an angry issue but he's not abusive. the trope is turns out he's your brother's campus's friend (your brother is Jihoon, Jaehyuk is Jihoon's friend)