Masato Kusaka/Zi-O

In 2003, Masato Kusaka (草加 雅人) was Kamen Rider Kaixa (仮面ライダーカイザ), until the creation of Another Faiz erased the Rider from history as well as undoing his death.

Switch On! 2011
Karin tries to relax on a rooftop, only for the man in the brown coat to run towards her and attempt to choke her. This man is revealed to be Masato Kusaka, who then tosses her off the roof, which Sougo, Geiz and Tsukuyomi witness from a hallway window nearby. They race to what they fear will be Karin's body, only to find she has been saved by Another Fourze.

Meanwhile in 2018, Tsukuyomi finds the abandoned building and enters it, only for Masato to follow her from the bushes. She finds Karin sitting on a bed and tries to convince her to leave but Tsukuyomi is suddenly ambushed by Masato. She draws out her Faiz Phone X and threatens to fire, only to be saved by a stranger who tussles with Masato.

Later Masato finally manages to get the stranger he's been fighting off of him, only to be revealed that it is the one person in the world Masato Kusaka hates the most...Takumi Inui aka Kamen Rider Faiz!

555・913・2003
Another Faiz reverts back to Another Fourze, using the Gatling Module to attack Zi-O and Geiz. Geiz summons the GhostArmor and the Parka ghosts attack Another Fourze, only for him to retreat and escape. Zi-O is still baffled by the fact that the Another Rider has two of the Heisei Kamen Riders powers at the same time. Back in 2018, Masato Kusaka is wondering what his hated rival Takumi Inui is doing, to which Takumi responds he is protecting Karin by stopping him. The two begin to fight again as Karin runs away with Tsukuyomi chasing after her, only to lose her once she is outside the building. Masato grabs Takumi upon losing Karin and tells him this has nothing to do with him and walks off.

At an apartment complex, the other Libra student is celebrating her birthday with her friends, only for the boy to attack her as Another Fourze and chase after her when she tries to run. Karin tells "Sakuma" to stop and lets the girl get to safety. Karin begs Sakuma to stop hurting others for her sake. Masato appears and grabs Karin, planning to kill her to put an end to this. Sakuma beats up Masato and prepares to snap his neck after headbutting him, only for Takumi to rush in and save Masato and get punched in the chest. Masato wonders why Takumi saved him, with Takumi answering that while he hates Masato sometimes, he still considers him a friend even though he hates to admit it. Sougo and Geiz arrive, but Sakuma flees, determined to keep Karin alive. Takumi gives Sougo his Faiz Ridewatch so he can stop Sakuma, but surprisingly Sougo entrusts the Ridewatch to Geiz, who heads off to stop Sakuma.

After defeating Another Faiz / Fourze, Masato leaves, with Takumi trying to follow him, but Masato won't accept it and stops him as he quietly walks off. Sougo smiles as he thinks that he has friends in Geiz and Tsukuyomi, though Geiz awkwardly feels uncomfortable about how Sougo is looking at him and walks away. Tsukuyomi asks Sougo once they get home if he returned the blank Ridewatches to Fourze and Faiz, to which a panicked Sougo runs out to return them to their rightful owners.

Personality
It is shown that Kusaka is not completely bereft of any positive and empathic qualities. As a result of a time paradox due to the creation of Another Faiz, and the fact that said Another Rider tried to keep his significant other alive, he is more willing to kill Karin out of mercy to relieve her of the life imposed to her by Sakuma. However, this doesn't change with the fact that his hostile relationship between him and Takumi is still intact.

Portrayal
Masato Kusaka is portrayed by Kohei Murakami (村上 幸平).

Appearances

 * Icon-zi-o.png Kamen Rider Zi-O
 * Episode 5: Switch On! 2011
 * Episode 6: 555・913・2003
 * Episode 6.5:The Secret of Fourze 555