Masato Kusaka/Kamen Rider Kaixa

Masato Kusaka, also known as Kamen Rider Kaixa, is the primary user of the Kaixa Gear and the tritagonist of Kamen Rider 555.

Despite being one of the main characters, he can hardly be considered a hero due to his manipulative and sociopathic tendencies, as well as his hatred of all Orphnochs, and is only really allied with the protagonists due to their shared opposition to Smart Brain.

When he was child, he was a crybaby and often to be helped by Mari, the reason of his desire of love to Mari. After the murder attempt on his classmate by Orphnochs, he developed a personal vendetta against them. However, his vendetta is not pure or just, as he will involve anyone to be in a dangerous position so he can gain the best advantage to destroy an Orphnoch.

In general, Kusaka is calm and polite towards everyone, except for Takumi. This, however is a guise to his true nature that even Takumi himself can see, he shows his true colors as a selfish, vindictive, and skilled manipulator who has no qualms of driving a wedge between Takumi and those around him like Kiba so he can have Mari for himself. With his twisted personality, he loves to betray anyone as long as he achieves his goals and doesn't seem to regret it, no matter the outcome. He will join any physical routine for testing his strength and often to lap his palms. His behavior to dust his palms is because remembering his incident from the Orphnoch's beginning attack, as such his hatred towards Orphonchs is so fanatical beyond belief, to the point he preys on the likes of Sawada or Takumi (who is also revealed to be one), regardless of whether they "have souls" or not and swore to destroy them all out of spite. Unlike his foil, Takumi, whose reasons of fighting Orphnochs for the sole purpose of protecting humanity, Kusaka's reasons are all motivated with petty vengeance.