Mizuhara is a member of the Human Liberation Front and a minor antagonist in Kamen Rider 555: Paradise Lost.
Mizuhara is seen at the beginning of the movie leading an operation to infiltrate Smart Brain's headquarters and steal the Emperor's Belt. However, the operations proves a failure when they are discovered by the Orphnochs and forced to retreat. Mizuhara returns to Paradise as the only survivor of the mission, with all of his teammates having been killed by Smart Brain. He is chastised by Mari for wasting human life, but Mizuhara responds by criticizing her for continuing to believe in Takumi Inui / Kamen Rider Faiz, who disappeared after an attack by Smart Brain's Riotroopers, telling Mari it's just a legend.
Later on, when Takumi does return with the Faiz Belt, Mizuhara attempts to kill him and steal the belt, shooting Mina when she takes the bullet for him. As Mizuhara runs away with the Belt, he is stopped by Yuji Kiba, who tells him he will not be able to use the Belt. Mizuhara attempts to shoot Kiba, but his bullets do nothing to the Horse Orphnoch. He is then swiftly killed when Kiba impales him with his sword.