Bleach: Cataclysm (漂白剤: 破局, hyouhakuzai: hakyoku), known otherwise as the Collapse (崩壊, hōkai), is the sequel to Bleach: War of the Worlds and comprises Part IV of Bleach (Kenji Hiroshi). A companion book titled Cataclysm was published shortly after the unveiling of Part IV, and a number of supplementary reference material was published shortly afterwards as well that either led up to or occurred during the Collapse. After an incident orchestrated by Kurokawa Kōhai that resulted in the catastrophic merging of the spiritual realms known as Horiwari, the Soul Society, Heisekai and Kohai Tochi, the survivors are struggling to rebuild whilst maintaining the Spirit Cycle of Souls. Into this new realm -- termed Reikai -- the past organizations battle amongst one-another for control. Kentaro Hiro