Kōga's a filler character from the Zanpakutō Unknown Tales arc, best known as the master of Muramasa.
He's got striking green eyes, shoulder-length black hair, and a long red ponytail with shorter red tufts on the left side of his head and bangs framing the right. When he served in the Gotei 13, he wore standard Shinigami robes along with a long red scarf, a light lavender obi, a beaded necklace with a pendant, and an ornate white headpiece called a kenseikan—the kind worn by nobility—which kept his ponytail in place. Those red hair tufts were a status symbol; he cut them off later after abandoning his Kuchiki clan standing.
After centuries of being sealed away, his appearance completely changed—what used to be a youthful, fit frame withered into an old man's body.
Personality-wise, Kōga started out dutiful and serious, genuinely committed to making his family proud and staying humble. But underneath that, he craved recognition for his abilities and effort. When he was betrayed and realized his old life was finished, something broke in him. He spiraled into anger and obsession with achieving greatness, eventually becoming arrogant to the point of dismissing everyone around him as worthless—even his own Zanpakutō, Muramasa.
Content compiled by AnimeList.moe from publicly available sources.
