10,000 years ago, there was a Battle Royale between 53 Undeads to determine which Undead's species will rule the Earth. In the end, Human Undead won and other Undeads were sealed......until today. The seal was accidentally broken and the Undeads were released. To counter this situation and seal all the Undeads again, a secret organization BOARD created the Rider system. 2 young men were chosen as Kamen Riders. Kenzaki Kazuma (Kamen Rider Blade) and Tachibana Sakuya (Kamen Rider Garren) fought together to protect humans from Undeads and sealed them. The battles became much more complicated when the mysterious 3rd Kamen Rider (Chalice) whose real identity and purpose remains unknown appeared. The 3 Kamen Riders who had different thoughts, fought against the Undeads, as well as their inner conflicts.
BOARD - A secret organization formed to protect mankind against mysterious beings known as the "Undead". Among their ranks are Kazuma Kenzaki (Blade) and Sakuya Tachibana (Garren) - two Kamen Riders who were created by BOARD after 52 of the Undead were accidentally released by the agency. After being kicked out of his apartment, Kazuma is offered to stay with aspiring journalist Kotaro Shirai in exchange for information on the Kamen Riders. Also living under the same roof is Hajime Aikawa - whose secret identity as Kamen Rider Chalice remains a mystery, as he fights alone and regards everyone, including the Kamen Riders, as his enemies.