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Icon-fourzeThis article is about an ally in Kamen Rider Fourze.

Kengo Utahoshi (歌星 賢吾, Utahoshi Kengo) is a Amanogawa High School student and the technician of the Kamen Rider Club. He was original pilot of the Powerdizer but his chronic headaches forced him to give the role up to Shun Daimonji. As such, Kengo became Fourze's main tactician in battle and is one of his strongest assets.


Core Child birth

The birth of the Core Child

Despite looking human, Kengo is actually a Core Child (コアチャイルド, Koa Chairudo), a construct of Cosmic Energy created by the Core Switch (コアスイッチ, Koa Suitchi), one of many mysterious crystal-like Switches that the Presenters sent across the cosmos in search of sentient life who can reverse engineer it. The Core Switch ended up on the moon where it was found by OSTO scientists Rokuro Utahoshi and Mitsuaki Gamou, both respectively creating the Astroswitches that function with the Fourze Driver and the Zodiarts Switches that forcefully evolved humans. A day before Gamou betrays him, Rokuro witnesses the birth of Kengo. Later, guilty of helping Gamou destroy the lunar station and killing Rokuro and unware of the infant's true nature, Kuniteru Emoto found Kengo and brought him to Earth.

Due to the development nature of a Core Child, Kengo often had headaches which he thought it was an illness of somekind. Therefore he often goes to the infirmary and dropping out his classes. Kengo uses this situation in order to stay in the school by have low attendance.

A year before the series started, Kengo received a letter and an Astroswitch from an anonymous person. The portal connecting to the Rabbit Hatch lunar base, which is all that remained of the OSTO complex, was opened in the locker in an abandoned club activity room when Kengo just so happened to throw the activated Switch inside. He discovered all about the Astro and Zodiarts Switches on the base and decided to follow through with his father's plans to fight the menace that is to come.

In his third year, having finished the Cosmic Switch, Kengo learns that Tachibana is the one who gave him the Gate Switch as he begins to learn more of his father from Emoto and Gamou during his trip to Kyoto. Eventually, Kengo learns that Emoto is both the Virgo Zodiarts and Tachibana as he reveals to the boy the full story behind his father's death and that the Horoscopes must be stopped from having all twelve switches. During the incident with the Gemini Zodiarts that followed, Gamou noticed a power emitting from Kengo. From learning the contents of Emoto's flash drive, Kengo learns that of his true nature as a Core Child and negates the 12 Horoscopes Switches, thwarting Gamou's plan to seek the Presenters.

Now able to use the Fourze Driver, Kengo reveals to the others that he must leave for the Presenters' planet with everything he has learned about Earth and humanity. Though acting emotionless, Gentaro saw through Kengo's attempt to lessen the pain by severing all ties and tells Kengo that he is still a person and a dear friend. However, as his departure would ruin everything he worked for with The Hole negated, Gamou uses his Sagittarius Nova to stop Kengo from leaving and crush the Core Switch, causing Kengo's body to dissolve into particles of light.

After Sagittarius Nova's defeat, upon finally accepting Gentaro's friendship, Gamou spends his final moments before being evaporated into cosmic energy to use Aquarius's power to recreating the Core Switch, resurrecting Kengo and reuniting with his friends. Kengo wakes up in his bedroom with no idea as to how he was restored but, with his illness gone and the Core Switch missing, reasons that he is now fully human before reuniting with Gentaro and Yuki at the bridge where their first encounter took place.


After graduating high school, Kengo attended Space Kyoto University and became a graduate student studying Cosmic Energy. After graduation, Kengo had followed in his father's footsteps by becoming a scientist, and was dedicated to contacting the Presenters in order to fulfill Rokuro and Gamou's dream. In 2018, Kengo was at mission control in Russia overseeing a space mission by Yuki while the Enigma device began to combine the world with the World of Build. Ultimately, the crisis was resolved within a day through the efforts of several Kamen Riders including Fourze. [Kamen Rider Heisei Generations Final: Build & Ex-Aid with Legend Riders]

After the Enigma crisis had wrapped, he was approached by Gentaro to help him stop Sanagiman and his followers, and when Gentaro chose to destroy the Fourze Driver in order to reach Saburo, Kengo accepted and understood his decision. Afterwards, as the rest of Kamen Rider Club lamented its destruction, Kengo was certain that as the Fourze Driver was Gentaro's friend it would always return when it was truly needed. [Kamen Rider × Kamen Rider Wizard & Fourze: Movie War Ultimatum]

Kamen Rider Zi-O[]

Tomoko, Miu, Kengo, Gentaro, Yuki, Shun and JK in Zi-O

Video Game appearances[]

Fourze with Kengo, Yuki, and Philip Travelers Senki

Kengo with Fourze, Yuki and Philip in Kamen Rider Travelers Record.

Kengo appears in the video game Kamen Rider Travelers Record.


Kengo is a loner with a strong will and wants to follow through with his father's plans to fight the Zodiarts. Because of this, he tries remains distant from people to not get them involved. Kengo does however accept help from Yuki Jojima and Gentaro after some convincing. He is willing to go to lengths that puts him and his health in danger which limits his actions. Kengo does not acknowledge the existence of the Kamen Rider Club and refuse to be a member of the Club. Though he is Gentaro's partner, he insists that Gentaro refers to him by his surname instead of his given name, and much to his chagrin, Gentaro refuses to do so.

During the early days, Kengo still refused to acknowledge the Kamen Rider Club even as the number of members grew and saw them as an immature group who were taking the occurring events too lightly. After he gets trapped on the Moon and seems certain to die, he initially despairs until he realizes that his father was in the same position but didn't give in to his fear and created the Fourze system. He then speaks to Yuki, who convinces him that despite their light-hearted demeanor's everyone in the club is working hard to help him in fulfilling his dream of fighting the Zodiarts, even in his absence. When he is finally saved, he acknowledges the existence of the Kamen Rider Club and joins it, accepting Gentaro and the others as friends (although he still refers to Gentaro as 'Kisaragi').

Although Gentaro's antics still irk him somewhat, he allows himself to be more open towards both him and the club, and as he sees how far Gentaro is willing to go to protect the school, his loyalty towards the Kamen Rider grows and starts to see him as a good friend rather than an unwanted partner.

Powers and Abilities[]


  • Core Child Physiology: Due to Kengo's true nature as the Core Child, he possesses a variety of powers after awakening.
    • Horoscope Switch Nullification: Kengo is able to nullify the power of all twelve Horoscopes Switches, dis-enabling Gamou's means of opening the Dark Nebula.
    • Energy Field Generation: Kengo can generate a impenetrable energy field that can block and deflect attacks.


  • High-Level Intellect: Kengo is intelligent by manner unrelated to school work, having a vast amount knowledge of the Astro and Zodiarts Switches and the Powerdizer which is useful in battle.
  • Master Tactician:
  • Master Engineer:


  • Low Stamina: Before Kengo's awakening, his body alone was highly unsuited for combat due to his spasms, which prevents him from using the Fourze Driver. To compensate, he uses the Foodroids and the Powerdizer to fight, but even then using the Powerdizer for a long period of time is an extremely difficult task for him due to the stamina needed to move. Because of his condition, the Fourze Driver was given to Gentaro and the Powerdizer to Shun Daimonji.


Fourze Arsenal[]

The entirety of the Fourze arsenal technically belongs to Kengo, constantly developing the system his adopted father made which he is meant as the Core Child to present to the Presenters.


Astroswitch Case
Main article: Astroswitch Case

Many items in the Fourze arsenal are linked up to the Astroswitch Case. The Case serves as a wireless computer that allows analyses, communication and other functions.


Main article: Foodroids

The Foodroids are functional spy devices and utility gadgets that aid the Kamen Rider Club. They have a limited amount of AI that allows them to respond to their human companions by way of performing tasks. They also on some occasions have shown initiative to perform tasks that fall under their set of abilities. They are activated by using specific Astroswitches.


Kengo is named after Takeshi Hongo (本郷 猛, Hongō Takeshi), better known as Kamen Rider 1, the original Kamen Rider. His name うたほし けんご (歌星 賢吾) being an anagram for the Rider's identity ほんごう たけし (本郷 猛) (Takeshi Hongou; Takeshi Hongou). This homage is alluded to in Fourze's Movie War Mega Max portion, Kamen Rider Fourze: Nadeshiko, Descend, where Kengo wears a makeshift Kamen Rider #1 costume as part of the Kamen Rider Club's Seven Legendary Riders cosplay.

Also, his surname Utahoshi contained the kanji "星", which translates into "star" to foreshadow his identity as the Core Switch.

His full name would translate as "Wise-Self Singing-Star".


  • According to Kamen Rider Zukan, it would be later revealed that Kengo and Yuki would become a couple following the five year time skip.[1]



Icon-fourze Kamen Rider Fourze
Kamen Riders
Main Riders: Gentaro Kisaragi - Ryusei Sakuta
Movie/Novel-exclusive: Nadeshiko Misaki - Tsubasa
Stageshow-exclusive: Kaizo Jingu - Tomoko Nozama - Shun Daimonji - Miu Kazashiro
Debatable Riders: Kouhei Hayami - Rider Hunter Boot
Transformation Devices
Fourze Driver - Meteor Driver- Nadeshiko Driver
Astroswitches - Astroswitch Case - NS-MagPhone
Astroswitch-related Weapons
Fourze Modules - Billy the Rod - Hee-Hackgun - Barizun Sword - Meteor Galaxy - Meteor Storm Shaft
Machine Massigler - Machine Meteorstar - Powerdizer
Kamen Rider Club: Yuki Jojima - Kengo Utahoshi - Miu Kazashiro - Shun Daimonji - Tomoko Nozama - JK - Chuta Ohsugi - Ran Kuroki - Haru Kusao - Saburo Kazeta - Rumi Komaki - Daita Kondou - Chikao Nezu - Miyoko Ohki
Ishinomori Characters: Inazuman - XVII - Skydain - Groundain - Black Knight - Inga Blink
Legend Riders: Momotaros - Urataros - Kintaros - Ryutaros - Tsukasa Kadoya - Daiki Kaito - Philip - Shotaro Hidari - Ryu Terui - Eiji Hino - Akira Date - Shintaro Goto - Haruto Soma- Kouta Kazuraba - Takeru Tenkuji - Emu Hojo - Sento Kiryu - Ryuga Banjo - Sougo Tokiwa - Geiz Myokoin
Others: Naomi - Owner - Ankh - Hina Izumi - Tsukuyomi
The Horoscopes: Sagittarius - Virgo - Leo - Libra - Scorpio - Cancer - Aries - Capricorn - Aquarius - Taurus - Gemini - Pisces
Zodiarts: Orion - Chameleon - Unicorn - Hound - Altar - Pyxis - Perseus - Lynx - Dragon - Pegasus - Cygnus - Coma - Musca - Hercules - Lepus
Others: Stardust Ninja Dustards
Foundation X
Lem Kannagi - Katal - Solaris - Controller Kiima - Suddendath Beta
Xatan - Eel - Gahra