Koromaru is a small Shiba Inu with gray and white fur, red eyes, and a curved tail. He wears a white vest, a red and black SEES armband on his front left leg, and a special winged collar that serves as his Evoker. This collar allows him to summon his Persona, Cerberus, without the need for a gun-like Evoker. He also bears tiny angel-like wings on his back, given to him by other party members.

Originally the loyal dog of a former SEES member, Koromaru continued to visit his master’s shrine and retrace their old walks even after the master’s death. He was discovered injured near the Naganaki Shrine by Akihiko Sanada during a Shadow hunt and, after recovering, was taken in by the group. He quickly became a full member of SEES, demonstrating intelligence, gentleness, and unwavering loyalty. His personality is inspired by the real-life dog Hachiko, and he embodies steadfast devotion. Though he cannot speak, Aigis often interprets his barks and gestures for the rest of the team.

In the film Winter of Rebirth, Koromaru stands alongside the other SEES members as they face the final battle against Nyx. His role is both that of a reliable combatant and a source of quiet emotional support for his companions. He forms especially close bonds with Ken Amada, with whom he shares a history of loss, and with Aigis, who acts as his translator. He deeply respects the team’s leader, Makoto Yuki, and is always ready to protect those he considers family.

Koromaru develops from a grieving animal clinging to his lost master into a confident and integral part of the team. His experiences with SEES help him move forward while still honoring his past. In battle, he wields a knife and uses his sharp senses to track enemies. His Persona, Cerberus, is a powerful dark‑type entity that complements his fighting style. Despite being a dog, Koromaru’s courage, intelligence, and loyalty make him a fully realized character whose presence enriches the story and the team’s dynamic.