Yu is quiet, polite, and calm for most situations. He seems to be emotionless and cold at times as well as occasionally deadpan. However he is shown to value the bonds of friendship between the members of the Investigation Team, is highly concerned about his friends and going to great lengths in order to help others. He has a dry sense of humor and sometimes does questionable things which he thinks are funny. He also seems a bit naive and oblivious to certain situations. His only insecurity is abandoment if he is separated from his friends he might withdraw into himself and lose the confidence that he usually potrays.