|Name: Mutsuki Kamijo|
|Designation: Kamen Rider Leangle|
|Weapons: Leangle Rouzer|
|Gear: Leangle Buckle, Green Clover|
|Mutsuki Kamijo is a troubled teenage high-school boy who was selected to become Leangle by the evil will of the Spider Undead. There was an instance, however, when Go Kiryu, the initial candidate to become Kamen Rider Garren, took it from him and, with the will of the Spider Undead's parasite spiders, used the system to assault Blade and Chalice. Although initially afraid of the dark when fighting the Mole Undead, Mutsuki overcame his fear when he saw the smiles on the peoples' faces he rescued. Unlike Blade and Garren, the first BOARD-created Riders, he gets no Jack form, but unseals other Undead to aid him, especially in the battle against the Keroberos Undead. This ability was removed from him when Joker was the only remaining Undead. Mutsuki's high-class Undead seem to be the kindest of all the high-class Royals. His Category King is a pacifist, his Category Queen has strong sense of honor and loyalty, and his Category Jack is really laid back, and sometimes lazy, only fighting to defend himself. All of them tend not to fight, unless it was necessary. And with the help of his Category King and Queen, only then he is able to suppress the power of the Spider Undead and properly seal him.
Mutsuki's girlfriend Nozomi provided a significant amount of help as well. Although she couldn't assist with fully suppressing the Spider Undead's power, her love for Mutsuki enabled him to at least partially resist the mind control. Mutsuki was able to figure out that Kamen Rider Chalice is really the 53rd Undead: Joker Undead and that he will become the strongest enemy when the rest of the Undead are sealed. He says to Garren that he will defeat him before that happens. Mutsuki at one time had all of Kamen Rider Chalice's sealed cards because of the Category King Cacacus Undead. He tells Mutsuki that he should stop caring for his girlfriend if he really wanted to become stronger. He continued being controlled by the darkness of the Category Ace until he sealed the Tiger Undead, who now encourages him to fight only for the sake of others. Eventually, when Kenzaki is not able to defeat Joker/Hajime, Mutsuki decided that it was he who would seal the Joker. He battled Joker with all his might and despite that, he lost the battle. He was last seen with his girlfriend playing some basketball.
In the Missing Ace movie, after Joker/Hajime was sealed, four years have passed and Mutsuki has tried to forget about being a Kamen Rider, working to have a normal life again. This was abruptly put aside when he witnesses the Category Ace of Clubs and was compelled to transform into Kamen Rider Leangle. Together with Kenzaki, Tachibana, Kotaro, and Shiori, they figure out that Glaive is really the Joker that everyone is looking for. But he still manages to take the ancient power and use it on the Riders. But thanks to Hajime's sacrifice, he, Blade, and Garren were able to defeat the Albino Joker and save the world once again.