Masato Kusaka

"You survived because of me. So having you die so I can live... Is just natural. I'll live... for "your" sake too."

- Masato's spirit trying to convince Faiz to give up.

Masato Kusaka (草加 雅人) was a member of Ryusei School who was capable of wearing the Kaixa Gear without disintegrating afterwards and the Gear's primary wearer as Kamen Rider Kaixa (仮面ライダーカイザ).

Kamen Rider Faiz
As stated above, Kusaka had a history with the Orphnochs which fueled his hatred for them. While originally acting friendly towards Takumi, he eventually showed his true colors and his motives were revealed.

Masato Kusaka is the only one to have worn all three of the Kamen Rider belts (Faiz, Kaixa and Delta). He wore the Faiz Gear to trick Yuji Kiba. He wore the Delta Gear to battle the Beetle Orphnochs (Rhinoceros and Stag).

Masato had a great deal more Orphnoch DNA implanted into him, allowing him to use the Kaixa gear safely for a time, but near the end of the series, it began to wear off, and using the Kaixa Gear was becoming increasingly harmful to him. In the end, his neck was snapped by Yuji Kiba, who claimed the Kaixa Gear as his own towards the end of the series and dies after all of his Orphnoch DNA ran out causing himself to disintegrate into dust with Takumi and the others being unaware of his death until later when his picture of a young Mari was found. This caused Takumi's anger to intensify as he cursed all Orphnochs including himself.

Rider War
Kaixa was one of the many Kamen Riders who fought in Rider War against  Decade appears at the beginning of Episode 1 of  Kamen Rider Decade . In a dream or vision of Natsumi Hikari, along with other Riders who were going to attack Decade, using his Side Basshar to attack Decade, but it was in vain, so he was defeated along with other Riders, leaving Kuuga as the only survivor, and then conclude the dream with a clash of blows Decade and Kuuga definitively.

The World of Kuuga
Kamen Rider Kaixa with the other Riders appears when Natsumi remember her dream of the Rider War ,the dream ends shock of fists between Decade and Kuuga.

Second Movement ♬ Prince Kiva
In Decade, Kaixa is a wildcard Kamen Rider who attacks Decade after he is taken to another world by Kiva-la. He is under the impression that Decade is a hindrance to his own agenda and seeks to take the Decadriver from him.

The Biting King's Qualifications
As Tsukasa is fighting against Kaixa in another dimension, the Beetle Fangire defeats Wataru and becomes the new Fangire king, claiming Kivat,He eventually concedes when Decade is returned to the World of Kiva.

The Destroyer of Worlds
Kamen Rider Kaixa reappears briefly in later airings of the series finale, using his Side Basshar to attack Decade and Wataru's group. He is seemingly killed in the chaos afterwards alongside many other Riders. In Kamen Rider Decade: The Last Story, Decade is shown to hold a Side Basshar card, labeled as a Kaixa card. Kaixa was presumably restored with all the other Riders after the destruction (and subsequent revival) of Decade ended the Rider War and the worlds were restored, though how he was still alive in the first place considering his fate in 555 is unclear.

OOO, Den-O, All Riders: Let's Go Kamen Riders
Kamen Rider Kaixa was part of a group of reinforcement riders led by Akira Date/Kamen Rider Birth to aid the primary riders in defeating the Rock Great Leader. All the Kamen Riders got on their bikes and performed the All Rider Break attack which destroyed the Great Leader.

Kamen Rider Taisen
"Why... Why does someone as hollow as you with nothing to protect get to live? Why do I have to die?!"

- Masato curses Takumi before he dies. At an unknown point of time, he as Kaixa were fighting the Horse Orphnoch, however he got himself killed while Faiz battled the Arch Orphnoch. Overpowered by the Horse Orphnoch and getting knocked out of his transformation, the Horse Orphnoch then threw a fireball at him to finish Kusaka off. Desperately reaching for the Kaixa Gear, he couldn't move anymore due to his burns and injuries. Faiz went to his side with Kusaka complaining on why Faiz survived while he had someone to protect. Crying out for life, he disintegrated.

Years later, while the Kamen Riders were fighting Badan, Masato's spirit appeared before Faiz and taunted Takumi into his feelings of guilt, having the Rider interfere with Wizard and X. However Keisuke and Haruto convinced him to move on as the spirit started to disappear.

Duel! The True Identity of Shocker's Great Leader
As mentioned by Kamen Rider 4, Takumi and all of his friends (except Naoya Kaido) died after the final episode of Kamen Rider 555. Masato is hypothetically mentioned as one of the casualties.

Kamen Rider Heisei Generations FOREVER
Kamen Rider Kaixa appears as a toy, when Sento and Sougo they find Ataru he brings them to his room which is filled with Kamen Rider memorabilia, with Sougo and Sento stunned to see toy versions of themselves. Ataru reveals that Kamen Riders are fictional.

Kamen Rider 555 Stage Show at Super Hero New Hero Legend
In a stage show where Kamen Rider Faiz and his allies are seen fighting their usual foes, Hakaider & Kamen Rider Ouja show up and ends up defeating him,, , , Kikaider, Kikaider 01, Inazuman, , , , Kamen Rider Ryuki, Kamen Rider Knight, Kamen Rider Zolda, & Kamen Rider Kaixa arrive to assist Kamen Rider Faiz.

Kamen Rider 555 video game
Kamen Rider Kaixa is playable along with Faiz and Delta in the Kamen Rider 555 video game.

Kamen Rider Battride War
Kaixa is introduced as one of NPC allies character.

Kamen Rider Battride War II
Kaixa is one of selectable summonned assist only Riders in Kamen Rider: Battride War II.

Kamen Rider: Battride War Genesis
Kaixa made his playable debut in Kamen Rider: Battride War Genesis.

On September 13, 2015, Kohei Murakami announced that he reprise his role as Kaixa in this video game onwards.

In this game, Kaixa's default playstyles is one of the well-round character to pick. However, when using his unique limited power up called Cursed Belt Mode, Kaixa sacrifices a small half of super meter in 20% (Starting Level) > 15 (Level 25) > 10% (Level 30 onwards) each level ups to utilize a powerful version of his special moves. He can also activate Cursed Belt Mode while during a normal attack string combo before performing a certain special move.

Due to Kaixa not having a final form, he is rides SB-913V Side Basshar Battle Mode as his final mode. Like Kamen Rider Birth Day in this final state, Side Basshar Battle Mode also cannot jump or guard unlike in TV series for some reason, as well as sacrifices amount of super meter when using Transportation Mode or Tag Partnered Double Rider Kick.

Kamen Rider Battle: Ganbarizing
Kamen Rider Kaixa is a playabled character in Kamen Rider Battle Ganbarizing.

Kamen Rider Buttobasoul
Kamen Rider Kaixa is a playable character in Kamen Rider Buttobasoul.

Kamen Rider Battle: Ganbaride
Kamen Rider Delta appears as a playable and support character in the video game Kamen Rider Battle: Ganbaride.

Battle Spirits
Kamen Rider Kaixa appears with other Kamen Riders and Monters in Battle Spirits.

Personality
"Those who hates me are just getting in the way."

- Masato revealed his dark side towards Takumi 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.

Like most Secondary Riders that came before and after him, Masato starts off hostile towards the main protagonist, but unlike the rest of them, he continues to remain as a nasty, cold-hearted and spiteful person and refuse to befriend the main rider. While this is somewhat understandable due to his past, it should be noted that Takumi tried to understand his pain and help him despite being treated harshly by Masato thus mostly making this moot. It is also notable that Masato spent a great deal wallowing in self pity while stating that others such as Takumi wouldn`t understand his pain despite Takumi trying to understand said pain showing hypocrisy. Whilst Masato discovered that Takumi is a orphnoch, he desperately wanted to kill him for his own purpose and almost sucessfully does so, until a another Faiz user stops him to do so. Masato says that he does not know any crimes that Takumi commited and he started hating Takumi a lot more. However, Kusaka's nasty and selfish personality is slowly revealed to Mari and Keitaro when Kiba tells them about what Kusaka did. His nasty personality is slowly revealed toward them while Kusaka slaps Mari in the face in front of Keitaro.

His cruelty towards every Orphnoch in the series is his fatal flaw, he refuses to determine of the alignment of other Orphnochs between good and evil and is deadset to eliminate them without second thought, it eventually lead to his karmic death at the hands of Kiba.

Arsenal

 * Kaixa
 * SB-913B Kaixa Driver - Kaixa's transformation device.
 * SB-913P Kaixa Phone - A sideflip "swing" cellphone device.
 * Kaixa Mission Memory - A small metallic card key containing the information of the Kaixa Armor.
 * SB-913C Kaixa Shot - Digital camera-shaped knuckle-duster.
 * SB-913B2 Kaixa Pointer - binocular-shaped pointer which enables to produce an energy drill deathblow.
 * SB-913X Kaixa Blaygun - A special weapon that is both a pistol, a dagger and a lightsaber.
 * SB-913V Side Basshar - Kaixa's sidecar motorcycle that can transform in a robot-like Battle Mode.
 * Faiz
 * SB-555B Faiz Driver - Faiz's transformation belt.
 * SB-555P Faiz Phone - The control unit of the Faiz Gear.
 * Faiz Mission Memory - A small metallic card key containing the information of the Faiz Armor.
 * SB-555L Faiz Pointer - A laser pointer which enables to produce an energy drill deathblow.
 * SB-555H Faiz Edge - A lightsaber-like sword that can be stored in Autovajin.
 * Delta
 * SB-333B Delta Driver - Delta's transformation device.
 * SB-333P Delta Phone - The walkie-talkie-shaped control unit of the Delta Gear and the first half of the Delta Blaster.
 * SB-333DV Delta Mover - The digital camcoder-shaped viewscreen and the second half of the Delta Blaster.
 * Delta Mission Memory - A small metallic card key which stores the information of the Delta Armor

Portrayal
Masato Kusaka is portrayed by Kohei Murakami (村上 幸平). As a child, he is portrayed by Yusuke Ito (伊藤 祐介). He later portrayed in . As Kamen Rider Kaixa, his suit actor was Makoto Ito (伊藤 慎).

Dub names
In the Korean dub of Kamen Rider 555 entitled Masked Rider Faiz (가면라이더 파이즈 Gamyeon Raideo Paijeu), which aired in South Korea, Masato Kusaka is renamed Sabino Kusaka (구사카 사비노 Gusaka Sabino). Ironically, his Korean dub name  happens to be shared with a group of horses, not to mention, he gets killed by Yuji Kiba, the Horse Orphnoch.