Shinjiro is Akihiko’s good friend, as well as a Senior in Gekkoukan High School. In battle, Shinjiro wields a hefty axe and relies on his brute strength. His Persona uses physical attacks.
Tough-talking, foul-mouthed Shinjiro was one of the original Persona users who made up SEES, alongside Akihiko and Mitsuru.
However, during one fateful mission his Persona went out of control and accidentally killed an innocent bystander: Ken’s mother. Shinjiro forced himself away from the group after the incident. He began skipping school and living as an outcast. He also started doing shady deals with Strega, in order to get drugs that could help control his Persona.
Shinjiro and Akihiko stayed in touch, but Shinjiro refused Akihiko's invitations to rejoin SEES until he learned that Ken had signed up for the group. He was fully aware of Ken's desire for revenge and ready to take responsibility for his actions. Though he put on a brave front, the guilt of having killed an innocent woman ate away at him.
On the second Full Moon mission after he rejoined SEES, Shinjiro meets Ken at the site where Ken's mother was killed. Shinjiro has no intentions to resist to Ken's attempt to extract revenge, but warns the boy that if he carries, he could end up just like Shinjiro. As Ken struggles to go through with his plan, the two are interrupted by Takaya. Takaya takes a shot at Ken and Shinjiro jumps in front of the bullet, ending his own life. He earns Ken's respect and inspires Akihiko's resolve with this final sacrifice. Later the members of SEES discover that the drugs Shinjiro was taking were slowly killing him.
During his final confrontation with Nyx, the Main Character hears Shinjiro's voice cheering him on, along with the voices of the living SEES members.