Despite his young age, Ken is very intelligent and mature. He is honest, diligent, and deeply caring towards his peers, particularly the members of SEES. He is very polite to others, and never misses a chance to show respect where respect is due. He has a strong dislike towards milk, but he forces himself to drink it so he can become taller. Ken notes that one of the reasons he uses spears in battle is so that he'll be on even ground with an adult. His reason for joining SEES is that he is lonely, vengeful, and desperate to avenge his deceased mother. Although Ken is very mature, he still has several qualities that fit with his age. He finds a role-model in Akihiko Sanada, whom he admires for his boxing and fighting talents, often referring to him as "Sanada-san" as a form of respect to his senpai. He also likes to watch a children's show, Phoenix Rangers, on Sundays.