Kaiwan

is one of the four guardians that guard the entrance to the Seireitei. He is the guardian of the.

Soul Society arc
Sōsuke Aizen hypnotizes him and two other Gatekeepers and used them to cause trouble for Ichigo Kurosaki and his friends. However, he is stopped by Jidanbō Ikkanzaka and Kūkaku Shiba.