Kei Nanjo

Games
Revelations: Persona: Playable Character Persona 2: Innocent Sin: Secret Character Persona 2: Eternal Punishment: Playable Character Persona 3: Mentioned by Mitsuru

Revelations: Persona

 * Initial Persona: Aizen Myouou
 * Ultimate Persona: Yamaoka
 * Weapons: Rifle and Broadsword

Persona 3
Kei does not appear in person in Persona 3, however, he is mentioned by Mitsuru Kirijo. Mitsuru explained that at one point the Kirijo family was part of the Nanjou family. The events of Persona 3 are in part caused by experiments done by Mitsuru's grandfather, however, it can be inferred that the events of Relevations: Persona could have played a part as well.