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 two points in the game, Kei suggests to let two innocent people die in order to save everyone else, the professor in charge of managing the DEVA System, who trapped himself in the machine along with Kandori to stop him from destroying reality and the true Maki Sonomura found after the Ideal Maki escapes from the party. However, these extreme choices are usually seen negatively by the rest of the party, with the latter leading to Masao punching Kei down.

Even with his seemingly collected and oftentimes stiff personality, Kei has a solitary weakness, and it is none other than the theme song often played at the chain of pharmacies owned by the Tadashi Family. This first manifested back in high school during the investigation on SEBEC, and haunts him up to adulthood. Kei feels that the silly lyrics hypnotize him, which invariably results in a total loss of composure.

 I do not have a preference with his voice,