The Monster That Lurks Underground is an event taking place during the Tōjū Campaign. It focuses upon 11th Division 3rd Seat Ikkaku Madarame, Hōzukimaru, 4th Division 7th Seat Hanatarō Yamada, and 8th Division Lieutenant Nanao Ise's fight against the Tentacle Tōjū in the underground waterway beneath the Seireitei.