Gin Ichimaru (市丸 ギン, Ichimaru Gin) was the captain of the 3rd Division of the Gotei 13 until he betrayed Soul Society, alongside Sōsuke Aizen and Kaname Tōsen. His lieutenant was Izuru Kira. He formerly served as the lieutenant of the 5th Division under Sōsuke Aizen and the 3rd Seat of the 5th Division under Shinji Hirako.

Gin with his right eye open. Gin is a thin, tall, and youthful man with very sharp features, giving him a skeletal appearance, and bears to ears length unusual silver hair (Light purple in anime). He keeps his eyes constantly narrowed to slits, rarely ever opening his eyes enough to reveal their bright sky blue-color.[2] He also keeps his face set in a wide mocking smile, which he only wipes off on rare occasions of annoyance, surprise, confusion, or even sadness.

In Hueco Mundo, his outfit, like Aizen and Tōsen's, had been modified since the three abandoned Soul Society. He now wears a long, white robe over his normal Shinigami hakama. The hilt of his Zanpakutō is visible sticking out from under the robe through the opening down to his waist. Later, Gin wears a white hakama like the Arrancar, instead of the black Shinigami hakama. Gin wears his robe open in a narrow 'V' down to his waist, closed to below the hips, and then open again to the hem, which falls about to mid-calf. His robe has long bell sleeves, into which he hides his hands. The lining of the robe and edges or layers of the under-robe(s) appear to be black. His Zanpakutō is not visible with this outfit.

Gin is a very mysterious man, since his almost constant smile and closed eyes, combined with his heavy use of sarcasm and mocking politeness, make it very difficult to discern his thoughts. In combat, he doesn't seem the least bit taken aback by the abilities of his opponent, even when they seemingly have an advantage. Many find his demeanor and appearance rather unsettling and there are very few who were willing to trust him even before he was revealed as a traitor. Gin is fully aware of the effect he has on others and more.