Ganju Shiba

Kūkaku's younger brother, leader of a Rukongai gang who rides around on the boar Bonnie. He hates Soul Reapers — until he learns who really killed his brother.

For years he believed the Soul Reaper Rukia had killed Kaien in cold blood. When he finds out who she is, he chooses to save her anyway: it is the act by which he becomes one of Ichigo's companions.