Whilst investigating the urban legends of the Undead, Kotaro Shirai stumbles upon the two Kamen Riders of BOARD.

BOARD is in pieces. Left reeling by Tachibana's betrayal, Kenzaki is forced to respond to another Undead attack.

Leangle attacks and overwhelms Kenzaki while Kiryu from BOARD reprimands Tachibana for leaving the battle.

Kiryu steals the Leangle buckle and transforms. Drunk with power, he attacks. His fate and Mutsuki’s are now twisted due to their newfound obsession.