Kaien sports a cheerful personality, yet can be serious at the same time. It can be said that he has a few odd personality quirks, such as his propensity to launch into tearful dramatics over the idea of being a poor parent to Yuki. Additionally, he enjoys ribbing his adopted children, particularly Zero, often mocking him about being a vampire as he refuses to consider Kaien and Yuki family, a fact which Kaien jokingly claims breaks his heart. He also enjoys cooking very strange food and making Yuki and Zero eat it.