Isshin Kurosaki (黒崎 一心, Kurosaki Isshin) is the father of Ichigo, Karin and Yuzu and head of the Kurosaki family. He is a skilled doctor, being able to perform almost any medical procedure except major surgery, who also runs his family's private clinic, the Kurosaki Clinic.
Little is known about Isshin's history, except that he was once a powerful Shinigami, though his division and actual rank are currently unknown. At some point he attempted to learn the Final Getsuga Tenshō by facing his Zanpakutō Engetsu. Whether he succeeded or was not able to learn this technique is unknown. About twenty years ago, he ceased being a Shinigami, losing most of his powers. Over ten years ago, Isshin encountered an imperfect Arrancar. He married Masaki Kurosaki and they had three children: Ichigo, Karin and Yuzu. Masaki was killed by the Hollow Grand Fisher when Ichigo was nine.
Isshin is also acquainted with Kisuke Urahara and Ryūken Ishida.
