Kei was forced to join in on the demon summoning game "Persona", which was started by a couple of his classmates. Kei chooses to just watch, as he doesn't really care about the result and feels that everyone was just feeding Masao and Hidehiko's stupid squabbles. Kei is the most logical member of the group, this being both a good and a bad thing. At points in the story, Kei might suggest something that may seem to be morally wrong. However, these extreme choices are usually seen negatively by the rest of the party. Even with his seemingly collected and oftentimes stiff personality, he still has some solitary weaknesses. While his parents are often away on business, Kei is looked after by Yamaoka, the Nanjo family butler. Since then he seems to have grown up under Yamaoka's watch, he considers him as more of a father figure than a servant. His distinctive trademark scarf with the number 1 printed on it symbolizes his desire to become the number 1 man in Japan.