Masao Inaba, known in Revelations: Persona as just Mark, is a graffiti artist who loves to dance. Masao considers himself to be the polar opposite of Nanjō, and the two of them do not get along. Masao has a crush on Maki and dutifully visits her in the hospital. He physically assaults Nanjō inside Maki's stasis room after Nanjō suggests killing Maki in order to sever her control over them.

He wields an axe as his melee weapon. He also uses shotguns. His initial Persona is Ogun. In addition to his school uniform, Masao wears a yellow tuque.

Masao appears in Persona 3 on the TV program 'Who's Who,' a show about previous Persona characters and what they are doing now. He is introduced as a "Man in his 20's with a yellow cap" and the program goes on to say that he is studying art overseas.

The fictional city in Persona 4 is named Inaba, a likely reference to Masao's family name.

His nickname Mark comes from his nickname when he was a baby "Makun"

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