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Icon-zo.png This article is about a rider in the film Kamen Rider ZO.

Masaru Aso (麻生 勝, Asō Masaru) is Kamen Rider ZO (仮面ライダーZO, Kamen Raidā Zetto Ō, Masked Rider ZO), the main protagonist in the Japanese tokusatsu movie Kamen Rider ZO.


Masaru was originally an assistant to Doctor Mochizuki until the doctor conducted experiments on him. Horrified at being made into a grasshopper-like cyborg, Masaru went into hiding in the mountains, but fell asleep for four years until he awoke with an unconscious urge to protect "Hiroshi". Finding the boy, he fought with the monster Doras who was attacking him, transforming into Kamen Rider ZO in the process. Impaling Doras on a metal pole, he followed the boy, Hiroshi's grandfather Seikichi Mochizuki recognizing him.

He again transformed into ZO to protect Hiroshi from the Koumori Man and Kumo Woman, monsters sent after Hiroshi by Doras. He defeated the Kumo Woman, but the Koumori Man took Hiroshi to his father Doctor Mochizuki's lab. Following, he quickly defeated the Koumori Man before the Neonoid, Mochizuki's ultimate creation, awoke, having imprisoned the Doctor for not letting it go free. ZO is defeated and absorbed by Doras, but hearing the music of Hiroshi's pocket watch distracts Doras, letting ZO break free and destroy it and the Neonoid. He managed to rescue Hiroshi but couldn't save the Doctor. Bringing Hiroshi back to his grandfather, he rides away on his motorcycle. Kamen Rider ZO

Though he hated Mochizuki for making him a cyborg, Masaru eventually forgave him before learning the man was telepathically communicating with him.[1]

Kamen Rider World

ZO and J, with Berry.

Later, ZO teamed up with Kamen Rider J. The two riders fought a gang of five revived monsters led by Shadow Moon: Sai Mutant, Cyborg Soldier Lv. 2, Agito, Garai, and Zu. Berry witnessed Shadow Moon's plot and is attacked by the mutants. Masato and his sister Ayumi stumble onto an injured Berry by chance and are chased by the revived mutant army as a result.

However, they are saved by the sudden arrival of Kamen Rider ZO on his ZO Bringer motorcycle, who thwarts off the monsters into a nearby abandoned warehouse. ZO is suddenly assisted by Kamen Rider J, who arrives into the warehouse on his J Crosser bike. The five mutants are defeated by the combined forces of the new Double Riders. The two are then challenged by Shadow Moon, who enlarges himself into giant proportions. J grows into giant size as well and fights off Shadow Moon by himself. Shadow Moon is defeated and peace returns to the day. Kamen Rider World

All Riders Vs. Dai-Shocker

Kiva, Black, Black RX, and ZO (left to right)

He arrives with the other Riders to fight Dai-Shocker's monster army, fighting Shocker Combatmen, the Butterfly Orphnoch, a Bakeneko, and the Slug Orphnoch before taking part in the All Rider Kick to destroy the Dai-Shocker Castle and Nobuhiko Tsukikage (Shadow Moon). He then became a Kamen Ride Card for Kamen Rider J as the giant Decade Complete Form to kick through to defeat Kingdark. The day saved, he left with the other Riders through a dimensional rift. Kamen Rider Decade: All Riders vs. Dai-Shocker

Let's Go Kamen Riders

ZO as seen in Let's Go Kamen Riders.

A mishap caused by the Greeed Ankh unintentionally altered the timeline which enabled Shocker to utilize a Cell Medal to create the Shocker Greeed which defeated the Double Riders and seemingly erased the legacy of the Kamen Riders from history. In 2011, after Kamen Rider New Den-O's attempt to repair the damage, he along with Kamen Rider OOO and M-Ankh awaited execution. However, it was revealed the Double Riders had their brainwashing removed by a Shocker scientist.

The Double Riders joined with New Den-O and OOO to fight Shocker's forces, but were eventually defeated. When the order was given to kill everyone, V3 suddenly appeared, asserting that there were more than four riders. V3 was soon followed by all the other revived riders that came after him, including ZO, as even though Rider history was changed, the people's memories haven't changed.

After the riders were united, they faced off against Shocker's Great Leader. Later, when joined by a force of extra riders, ZO and all the other riders got on their motorcycles and performed the "All Rider Break", ramming into the Rock Great Leader and defeating it once and for all. OOO, Den-O, All Riders: Let's Go Kamen Riders

Super Hero Taisen

14 Showa KR,9 Heisei Rider & 1 Neo-Heisei Rider(with Accel).jpg

ZO was among the Kamen Riders caught up in the 'Super Hero Taisen' incident. He was presumably sent to the dimensional rift, under the pretense of being defeated, by Captain Marvelous while he was apparently hunting the Riders. When his and Tsukasa's ruse was revealed, ZO and the other Riders appeared through the dimensional wall. ZO then fought alongside all the other Kamen Riders and Super SentaiIcon-crosswiki.png against Dai-Shocker and Dai-Zangyack's Shocker-Zangyack Alliance. Kamen Rider × Super Sentai: Super Hero Taisen

Kamen Rider Taisen

As one of the 15 Showa Riders, ZO fought in the battle against the 15 Heisei Riders in Zawame City. At some point during the fighting, he was defeated by a Heisei Rider, turning into a Lockseed.

ZO was later released with all the other sealed Riders by Kamen Riders Gaim and ZX. United, all 30 Kamen Riders teamed-up to take down the revived Badan Empire.

After Badan was defeated, ZO fought with the Showa Riders in a final showdown against the Heisei Riders. ZO took on Agito, striking each other with their Rider Kicks and falling to the ground after their power collided. The battle was ended when Rider 1 and Gaim reconciled on the differences of the two sides of Kamen Riders. Heisei Rider vs. Showa Rider: Kamen Rider Taisen feat. Super Sentai

Super Hero Taisen GP Kamen Rider 3Icon-crosswiki.png

Due to the timeline alteration caused by Shocker, ZO became one of the brainwashed Riders in that timeline, donning the name of Shocker Rider ZO.

Following the Rider Grand Prix in which Drive emerged victorious over Kamen Rider 3, who was promptly integrated into the Great Leader of Shocker's Rider Robo form, ZO was among the Riders who appeared to attack Zeronos Zero Form and Denebick Buster only to be fought off by the turncoat BOARD Riders: Chalice, Leangle, Blade and Garren. Ultimately, the Double Riders 1 and 2 made their appearance having survived their apparent demise from within the Rider Robo, and broke Shocker's brainwashing on the fallen Riders, enabling all Riders to unite in a final battle against Shocker.

Unfortunately, ZO was among the Riders whose existence was erased by the Rider Robo. This fate, however, was rendered moot when the Rider Robo was finally destroyed by Shurikenjin TridoronIcon-crosswiki.png, restoring ZO's place in history.

Kamen Rider ZO

Kamen Rider ZO

Kamen Rider ZO

An X-Ray Diagram of Kamen Rider ZO

Rider Statistics:[2][3][4]

  • Rider Height: 193 cm
  • Rider Weight: 83 kg

Ability Parameters:

  • Maximum Jump Height: 130 m[2][3][4]
  • Maximum Running Speed: 100 m per 1.2 seconds[note 1]

Masaru is capable of transforming into Neonoid #1 (ネオ生命体第1号, Neo Seimei-tai Dai 1-gō), a mutant that partially incorporates the grasshopper gene and machine called ZO, who would be later called Kamen Rider ZO. Masaru first gained this ability after being forced to undergo surgery and genetic modification by Doctor Mochizuki, who was driven by madness. At first, he had no control over the transformation and it was triggered by emotional stress. A bolt of lightning somehow corrected this problem while putting Masaru in a coma. During his four year coma, the Red Core (レッドコアReddo Koa) on his waist absorbed the biological energy of nature to enhance ZO's power to an unknown limit.

Having undergone organic remodeling, Masaru has a strong body and special abilities even before transformation. He has extraordinary durability, as seen when he withstood a direct hit from Doras's Moleculaser, and was able to transform immediately afterward. ZO also possesses a healing factor to some degree, as he is able to recover from injuries in a short period of time. Masaru has several telepathic abilities. He can telepathically communicate with grasshoppers, which enables him to see the locations where they have been or listen to the conversations of those around the insects. Doctor Mochizuki was communicating with him psychically over long distances as well. He also repaired Masaru's broken pocket watch through unknown means.

Upon transformation, Masaru's body resembles a locust, enveloped in a dark green armored shell made of enhanced biological tissue covering the entire body with golden biological lines. ZO's strength is able to crush special alloys up to 20 cm thick and he can scrap up to 50 cars in a single blow.

Special Attacks

  • ZO Punch (ZOパンチ, Zetto Ō Panchi)
  • ZO Kick (ZOキック, Zetto Ō Kikku)


Break Toother

Break Toother

Another of ZO's features within his insectoid head is the Break Toother (ブレイクトゥーサー, Bureiku Toūsā), a breathing apparatus stored around the mouth plate that releases vapors from holes in the golden lines on the back of his head, bearing a resemblance to fangs when extended.


Main article: Z-Bringer

ZO also rides on the Z-Bringer (Zブリンガー, Zetto Buringā), built by Dr. Mochizuki. Though resembling a regular motorcycle, the Z-Bringer changes along with ZO with ability to reach speeds up to 1300 km/h and resist heat up to 1000 degrees. ZO can use the Z-Bringer to execute the Z-Bringer Attack (Zブリンガーアタック, Zetto Buringā Attacku) Rider Break.

Legend Rider Devices

KamenRide: ZO

KamenRide: ZO (カメンライドZO, Kamenraido Zetto Ō) is the Rider Card which contains the power of Kamen Rider ZO. In All Riders vs. Dai-Shocker, Decade Complete Form Jumbo Formation performed the Final Dimension Kick, a variation of the Dimension Kick, transforming the Shōwa Riders, including ZO, and Heisei Riders into Kamen Ride cards for Decade to travel through as opposed to Final Attack Ride cards before hitting the target.

In theory, this card would allow Kamen Rider Decade to transform into ZO.

Final AttackRide: ZO

Final AttackRide: ZO (ファイナルアタックライドZO, Fainaru Attakuraido Zetto Ō)

Kamen Rider ZO Lockseed (仮面ライダーZOロックシード, Kamen Raidā Zetto Ō Rokkushīdo): A Lockseed bearing the likeness of Kamen Rider ZO, created when ZO was defeated in the battle between the Showa Riders and Heisei Riders. Heisei Rider vs. Showa Rider: Kamen Rider Taisen feat. Super Sentai The core image depicts ZO's waist while the lid backside image depicts Berry. When inserted into a Sengoku Driver or when channeled through the Showa Rider Lockseed, it would allow an Armored Rider to assume ZO Arms (ZOアームズ, Zetto Ō Āmuzu). It is styled for Zangetsu and Mars in the toyline.

  • Transformation: ZO Arms: Daijizen Neo Seimeitai!
    • Squash: ZO Punch (ZOパンチ, Zetto Ō Panchi)
    • Au Lait: Z-Bringer (Zブリンガー, Zetto Buringā)
    • Sparking: ZO Kick (ZOキック, Zetto Ō Kikku)

"(Digital beeping) ZO!"
―Activation announcement[src]

ZO Ridewatch (ZOライドウォッチ, Zetto Ō Raidowotchi): Based on Kamen Rider ZO, this Ridewatch would provide access to the ZOArmor. It is dated 1993.

Other Appearances

Although Kou Domon has never returned to portray the character Masaru Aso, a generic "Kamen Rider ZO" character has appeared in later Kamen Rider live action productions.

Later Appearances in Kamen Rider/Super Sentai live action productions

Zyuranger Stage Show at Super Hero Korakuen Yuenchi

In a stage show where the Zyurangers are seen fighting their usual foes, Neonoid shows up and ends up defeating them. ExceedraftIcon-crosswiki.png Kamen Rider ZO, Red HawkIcon-crosswiki.png, White SwanIcon-crosswiki.png, Five BlackIcon-crosswiki.png & Black TurboIcon-crosswiki.png arrive to assist the Zyurangers.

Let's Go Kamen Rider net movies

  • In the 4th net movie Listen Quietly! The Tragedy of the 20th Anniversary Rider!, ZO was doing a speech to commemorate the film and the franchises 40th anniversary. The speech quickly became a rant about how his film came out in 1993 rather than 1991 and yet is considered a 20th anniversary production when it was the 22nd year of the franchise, how people confuse him with Kamen Rider J despite having a different look, the pronunciation and meaning of his name, how his enemy Doras was the villain of Movie War 2010 and the fact he didn't get to fight him. He then screams that he demands to know who is responsible for his misfortune but then he is dragged off the stage by 1, 2, OOO and Den-O.

Video Games

The Masked Rider: Kamen Rider ZO

Through his appearance in ZO, Masaru Aso/Kamen Rider ZO is featured in The Masked Rider: Kamen Rider ZO.

The Great Battle IV

  • In The Great Battle IV, Kamen Rider ZO is a playable character and one of the pilots of the Compatible Kaiser along with Ultraman, original hero Fighter Roar and the Victory 2 Gundam (portrayed as human-sized here).

All Kamen Rider: Rider Generation

  • Kamen Rider ZO is also a playable character in the 2011 Nintendo DS video game All Kamen Rider: Rider Generation and Rider Generation 2 for the Sony PSP and Nintendo DS.

Kamen Rider Battle: Ganbaride

  • Kamen Rider ZO is a playable character in Ganbaride.

Kamen Rider SD

ZO SD.jpg

  • Although ZO didn't show up in any Kamen Rider SD medias like manga, OVA or video games. His SD counterpart was released however as a soft vinyl figure in one of the SD toylines along with Kamen Rider Shin.

Behind the Scenes


Kou Domon, still in costume as Masaru Aso, is interviewed on TV.

In Kamen Rider ZO, Masaru Aso was portrayed by Kou Domon (土門 廣, Domon Kō), who later played SigIcon-crosswiki.png in Blue SWATIcon-crosswiki.png. As Kamen Rider ZO, his suit actor was Jiro Okamoto (岡元 次郎, Okamoto Jirō).

Rider No.

As the leading Rider protagonist of Kamen Rider ZO, Masaru Aso (Kamen Rider ZO) is labeled Kamen Rider #14 (仮面ライダー14号, Kamen Raidā Jūyongō) and Showa Rider #14 (昭和ライダー14号, Shōwa Raidā Jūyongō). Quiz! Decade Countdown!!

Concept Art

Early Storyboard art

  • Various art books reveal an earlier concept for ZO was that he was an alien warrior from outer space who came to Earth to stop an invasion.



  • In the earliest trailer which was titled "Masked -Rider-", ZO's suit looks completely different from the film version. Many years later, Keita Amemiya finally confirmed it is actually Kamen Rider Black's suit since at that time they didn't have a final design.[6]

Scrapped Development


  • Keita Amemiya had designed ZO's upgraded form. In this form ZO was wearing a red scarf, and his limbs and belt becomes silver. But it has never been adopted because the other producers changed their mind.

ZO power up unused concept.jpg


  • In reality, the best indicators for which is ZO and which is J is that J has stripes in various shades of green and a seashell-like gem on his waist while ZO has a round gem with gold vein-like patterns on his body.
    • In some official material, ZO would be depicted with his Break Toother extended, in order to further distinguish him from J.


Main article: Masaru Aso/Appearances

See also



  1. 300 km/h[5]


Icon-shin.png Icon-zo.png Icon-j.png The 90's Movie Trilogy
Kamen Riders
Shin Kazamatsuri - Masaru Aso - Kouji Segawa
Z-Bringer - J-Spirit - J-Crosser
Shin: Ai Asuka - Daimon Kazamatsuri - Takuya Yuuki - Shiin Kazamatsuri - Sarah Fukamachi
ZO: Hiroshi Mochizuki - Seikichi Mochizuki - Doctor Mochizuki - Reiko - Kuroda - Nishimura - Miyazaki
J: Kana Kimura - Earth Spirits - Berry
Foundation (Shin): Iwao Himuro - Goushima - Giichi Onizuka
Neonoid (ZO): Doras - Koumori Man - Kumo Woman
Fog (J): Fog Mother - Agito - Zu - Garai