Kei Karasuma/Missing Ace

Kei Karasuma (烏丸啓) is the original chief of BOARD who created the Rider systems.

Kamen Rider Blade: Missing Ace
In Missing Ace, 4 years after the series ends, he and Sakuya discover The Stone of Relief and cracked the seal. Later, he tried to cover all 53 cards (including Black Joker) after they witness the creation of Vanity Card (which indicates the presence of another Undead), when Albino Joker appeared and unsealed Undeads, who attacked and killed Karasuma. His death was covered up by Sakuya Tachibana from everyone except the Kamen Riders and Amane.