Shūkai (Mastered Release) is the release of a Zanpaktou that goes beyond the Bankai release. This form can only be used when the blade and its master have synced their souls into one and have gone through extensive training, they can unlock Shukai. When Shukai is used, the user starts to develop physical characteristics of their blades' spirit. For example, Seireitou's Zanpaktou's spirit is Kyuubi no Yoko. When Seireitou uses Shukai, his upper half of his body grows red fur around him, and grows 9 Tails like Kyuubi. At this form, the blade combines with the user, into one being of immenese power. When Shukai is brought to a certain level of mastery, it can be evolved into stronger forms, like Shukai Lv.2 or Shukai Lv.3. Shukai can only last for a few minutes depending on the mastery of the