Kenzaki was a man who was orphaned at 11 by a fire. Years later, the organization BOARD scouted him out, making him a candidate for Rider System-02, Blade. He displayed unusually high fusion coefficiency with the Undead involved in the Rider system, and eventually became the partner of Rider System-01's user, Sakuya Tachibana.As the Battle Fight continues, Blade acquires the Rouse Absorber developed by Kei Karasuma, using it at first to assume Jack Form with the Category Jack of Spades Fusion Eagle, and then King Form, with the power of all 13 Category Spades Undead instead of merely the Category King of Spades Evolution Caucasus. This increased King Form's power at the cost of eventually turning Kenzaki himself into a Joker Undead. He uses this in the finale to allow Hajime/the Black Joker to continue living as a human, yet with him as the Navy Joker and to stay away from Hajime.
All Your Powers Combined: Not only does King Form allow Blade access to all Category Six cards, giving him control of all four elements, it also uses the power of all thirteen Category Spades Undead.
Dangerous Forbidden Technique: King Form slowly turns Kenzaki into a Joker the more he uses it. He uses this to his "advantage" by overusing it in the finale to save Hajime. Since two Jokers exist, the Battle Fight can continue indefinitely.
Lightning Blast: Combines the power of the Category Five Kick Locust and Category Six Thunder Deer to execute a lightning-powered flying side kick.
Lightning Slash: Combines the power of the Category Two Slash Lizard and Category Six Thunder Deer to execute a lightning-powered slash with the Blay Rouzer.
Lightning Sonic: Combines the power of the Category Five Kick Locust, Category Six Thunder Deer, and Category Nine Mach Jaguar to execute a high speed version of Lightning Blast.
Royal Straight Flush: King Form's most powerful finisher. Combines the Category Ten Time Scarab, Category Jack Fusion Eagle, Category Queen Absorb Capricorn, Category King Evolution Caucasus, and Category Ace Change Beetle to deliver a deadly strike with the King Rouzer.
Straight Flush: Combines the Category Two Slash Lizard, Category Three Beat Lion, Category Four Tackle Boar, Category Five Kick Locust, and Category Six Thunder Deer to execute a double sword strike with the King Rouzer and Blay Rouzer.
Four Cards: Combines all Category Six Cards (Thunder Deer, Fire Fly, Tornado Hawk, and Blizzard Polar) with the Category King Evolution Caucasus to deliver a powerful elemental slash.
Sakuya Tachibana was the second person chosen by BOARD to use the Rider System-01, Garren, after the first user Go Kiryu was determined to be too incompatible. Tachibana fears that continuous use of the system would erode his DNA, which is why he attacked Kei Karasuma, seemingly releasing Undead and betraying BOARD. Later, he manages to be manipulated by Isaka/Peacock Undead for the latter's sinister plans, until it is revealed that Isaka killed his girlfriend Sayoko Fukasawa. With this he defeats the Undead and in repentance takes Mutsuki/Leangle under his wing. In the Final Battle, he fights the Category King of Diamonds Giraffa, until it ends with Garren nowhere to be seen and the Giraffa Undead sealed. But returns in the finale
Burning Smash: Combines the Category Five Drop Whale and the Category Six Fire Fly to execute a fire-powered drop kick.
Burning Divide: Combines the Category Five Drop Whale, Category Six Fire Fly, and Category Nine Gemini Zebra to execute a fire-based drop kick that produces a clone, granting additional power.
Burning Shot: Combines the Category Two Bullet Armadillo, Category Four Rapid Pecker, and Category Six Fire Fly to shower foes with multipleflamebullets.
Two unnamed combos, one combining the Category Six Fire Fly and Category Three Upper Frog to deliver a fire-powered uppercut, and one combining the Category Two Bullet Armadillo and Category Six Fire Fly for shooting fireballs at the ennemy.
A mysterious photographer living with the Kurihara family, with the ability to become a Kamen Rider. In reality, the alter ego of the Black Joker Undead, whose victory in the Battle Fight would cause The End of the World as We Know It. He uses the Category Ace of Hearts Change Mantis to assume the form of Kamen Rider Chalice, and the Category Two of Hearts Spirit Human to assume a human form. The combination of the Mantis Undead's fighting spirit and the Human Undead's compassion helped to control his natural impulses as the Joker. After witnessing a man's death at the hands of one of the Royal Club Undead, he vows to protect the man's family adopting the persona of Hajime Aikawa. After the Caucasus Undead steals most of his cards, including the Category Ace of Hearts Change Mantis, he begins to regress into his Joker form, with Leangle unsealing his cards in an attempt to control him. The Joker continues to rampage, however, until he acquires the Evolution Paradoxa card, allowing him to access Wild Form. By series end, with all other Undead sealed, he regresses to his true nature as the Black Joker, dooming life on Earth. Eventually Kenzaki takes it upon himself to defeat Hajime, not by sealing him (though this provides the plot of the Missing Ace film), but by becoming a Joker himself, allowing Hajime to resume living as a human with the Kuriharas.
Voluntary Shapeshifting: The Chalice Buckle can be used to facilitate this; Hajime normally uses it to transform into his Rider form or his human form, but it can be used to transform into other Category Heart Undead.
Mutsuki is a trouble highschool boy chosen by the evil Spider Undead to become Leangle. Unlike the other two BOARD-based Rider Systems, Leangle has no access to Jack Form, yet can unseal Undead to aid in battle. While his Ace Undead is evil, his Royal Club Undead seem to be kind: Category Jack/Elephant Undead does not wish to fight much, Category Queen/Tiger Undead has a strong sense of justice, and the pacifist Category King/Tarantula Undead aids the Riders in his human persona Noboru Shima. With the sacrifices of the Tiger and Tarantula Undeads, Mutsuki is able to overcome the Spider Undead's evil influence. With Garren nowhere to be found after the Giraffa Undead's unsealing, he assists Blade in dealing with the Darkroaches as Blade himself goes and faces Hajime as the Joker.
Lightning Bruiser: His Ace Form has the best stats of the four. Comparatively, his SIC-figure-only Jack and King forms are...
Mighty Glacier: Not seen in-show, but the stats and appearance of his SIC-only Jack◊ and King◊ forms indicate that it trades speed and agility (Leangle Jack's jump height is listed less than one-fifth of Blade Jack's!) for sheer overwhelming power.
Missing Ace shows the opposite to be true, as well, as explained above.
The Board Of Archaeological Research Department developed technology to combat the Undead, making the first two Rider Systems and their support gear. Is destroyed in the first episode after Tachibana's apparent betrayal.
Kei Karasuma | Actor: Kazuhiro Yamaji
A professor who created the Rider Systems 01 (Garren) and 02 (Blade), as well as 03 (Leangle) under the directions of Isaka the Peacock Undead. He entrusted the Rouse Absorbers to Noboru Shima, despite knowing of the latter's nature as an Undead. He also knows of the secret that Blade's King Form has...
Yoshito Hirose | Actor: Junichi Haruta
Shiori's father, who unsealed the Undead, seemingly being killed in the process. Turns up later seemingly alive, only for him to be revealed as the Trial B Undead, originally programmed by the real Yoshito Hirose to protect his daughter. However, Tennoji reprogrammed him to monitor the Battle Fight, but after sacrificing himself to protect Shiori from Trial G, he remembers his true purpose.
Chairman of the BOARD organization. Set up the Battle Fight in his favor, and created the hybrid Undead Category Ace Kerberos, wishing to use it to rule the world. While he manages to create (and eventually fuse) with Kerberos, he is killed by the Giraffa Undead after his defeat at the hands of the Riders.
A God Am I: His ultimate goal is to win the Battle Fight and gain the power to reshape the world in his own image.
Big Bad: While not the final villain, everything bad in the series is pretty much his fault.
The Man Behind The Monsters: Controls some of the Undead directly and a few of the Trials, but arranged the release of all of them in the first place.
One-Winged Angel: Merges with the Kerberos Undead in order to be the victor of the Battle Fight.
Villainous Breakdown: He has a complete mental breakdown upon his defeat, ranting about his "new world" and how the two remaining Undead must be sealed so it can happen.
Undead are the kaijin of the show. There are 52 or rather, 53 Undead each competing in the Battle Fight, with the victor's species gaining dominance over the world. The winner of the previous Battle Fight ten thousand years ago was the Human Undead, resulting in the dominance of humanity.Most of the "numbered" Undead are only capable of speaking their own language; however, those belonging to the so-called Royal Club can take on human disguise and speak human languages like Japanese. Their motivations are diverse and complex, from one fond of humanity (Tarantula Undead/Noboru Shima) to one with very sinister designs (Spider Undead).
Lethal Joke Character: Somehow, the extremely lowly Human Undead was the one that won the previous Battle Fight.
What makes this even more amazing is Hajime said the Human Undead sealed him the last time. Somehow the Human Undead sealed the Joker!
Mythology Gag: Not only is there the Spider Undead, serving as a minor antagonist throughout the series, but the first Undead we see Garren and Blade fight is the Bat Undead. Both are references to the first Kamen Rider monsters.