Icon-amazons.png This article is about a/an ally/monster in Kamen Rider Amazons.

"Does it hurt...Chihiro?"
―Iyu's words after protected Chihiro at her own will[src]

"Target Confirmed."
―Iyu's pre-Battle catchphrase after detecting Amazons .[src]

"Chihiro...I'm so happy..."
―Iyu's last words before her second death.[src]

Iyu Hoshino (星埜 イユ Hoshino Iyu) was a human female who was killed and revived as a "Sigma Type Amazon", she is able to transform into Crow Amazon (カラスアマゾン Karasu Amazon)


Like Jun Maehara, Iyu is a Sigma type Amazon – an Amazon developed by implanting Amazon Cells into a dead body. She, along with the rest of her family, was killed and eaten by her father, who turned into a new type Amazon when celebrating his birthday. She was found by Takeshi Kurosaki in a raid at her home where the murders occurred. She was the least damaged compared to other family members and was still alive when Haruka ended his father. Initially taken back to 4C headquarters for medical attention, she died on the way and the plan changed to have her resurrected as the second and last Sigma type Amazon instead, stating that Yugo Tachibana had one final permission to use that technology to compensate the lack of 4C fighter Amazon (after Mamoru/Mole Amazon and Haruka Mizuhara/Amazon Omega left).

Soon after she was "completed", she was sent to work with Team Kurosaki to exterminate Amazons, acting mainly as a sensor to confirm targets until deployed at the front lines.

Chihiro/Amazon Neo developed an unhealthy obsession to her since they first met, due to him not feeling the urge to eat her like he did other humans, (revealed later to his disappointment, that it was simply because she was literally a walking dead) stating that as long as he was with her, he can be human. As such, he was overly protective to her, even joining 4C on the condition that they would treat her as humanly possible. Understanding his request, Yugo Tachibana put him in Kurosaki Team, pairing him with her to bolster the team's offensive capabilities against Amazons.ORPHANS

Awakening Iyu's "Human" side

When Haruka Mizuhara came for her to "let her rest", Chihiro protected her valiantly. Despite of all these, Iyu stayed on her emotionless, duty-bound personality. When Chihiro started to show urge to eat human, Iyu immediately identified him as enemy and severely wounded him.PERSONA NON GRATA

Even so, Chihiro's feeling didn't waver. He took her out to an amusement park, attempting to make her "more human" by having her imitating normal people. He even bought her new clothes and food, and make photos with her, until Takeshi Kurosaki found him by tracking signal from Iyu's bracelet.QUO VADIS?

Reunion of Alpha and Neo

Chihiro later asked their mutual friends, Hiroki Nagase, about how Iyu was when she was alive. Apparently, Iyu was a cheerful girl, who laughed a lot and excelled at baking cake. Hearing this, he immediately bought her a cake. Unfortunately, he tripped when he was about to give it to her, slamming it to her face instead. This made her remember a part from her past, however she was still emotionless.SCHOOLDAYS

However, when Chihiro said that he met her former classmate, Iyu started to show her desire to recall her memory. She then went to her hometown, where he met Hiroki Nagase and went to various places of her past. During this trip, she found enemy Amazons and engage them, however she was overwhelmed and rendered incapable to fight. Shortly, Chihiro came to rescue, however his previous experiment also crippled him. Fortunately, Jin Takayama/Amazon Alpha came and defeated the enemy Amazons.THE THIRD DEGREE

Reawakening of the Origin

Iyu was present in the Kurosaki Team office when Chihiro was about to be put to stasis. Chihiro asked about whether Iyu had something to say in their possibly last interaction, however Iyu stayed silent, even after Chihiro showed her their pictures in amusement park and told her that he had fun. Right before entering the stasis, Chihiro kept remembering their moments together, finally realized that he wanted her so much. This made him berserk, assuming his true Amazon form (driverless), killing many people in that room. When Takeshi Kurosaki commanded her to kill Chihiro, Iyu didn't budge, restated what Takeshi told her earlier, that he was different than the kind of Amazon they hunted.

However, Chihiro unintentionally wounded Iyu as well. The sound of Iyu's blood dripping finally stopped Chihiro's rampage. After he ran away, Takeshi unleashed his anger to Iyu, told her to forget everything he said and that they would hunt Chihiro. Iyu, still emotionless, answered with a single firm affirmative.VANISHING WINGS

Hunting Chihiro

Due to his armlet being damaged during his rampage, the group is forced to rely on Iyu to sense his cannibalistic instinct. Later in the night, she finds Chihiro nearly succumbing to his hunger, stalking a woman when her voice brings him back to reality. Team Kurosaki then engages him, though Chihiro is reluctant to fight back against her, even lamenting that he is now the kind she hunts. When she is about to finish him, Nagase holds her back, telling her to stop and giving Chihiro the opportunity to flee. WAY TO NOWHERE While taking a break, Iyu is pulled aside by Nagase who has been trailing Team Kurosaki, trying fruitlessly to convince her not to kill Chihiro, giving her the picture that she had taken with him when they were at the Amusement Park. However, Kurosaki knocks him away, telling him that Chihiro will eat someone before telling Iyu that she has "garbage" in her hand, which she crumples and throws to the ground, taking her leave, much to Nagase's disappointment.

When Team Amatsuki reports that they found Chihiro who tried to flee from the blockade, Kurosaki tells her to go on ahead. She finds Chihiro at a field, stating that she has found her target. Chihiro tells her that if she wants to kill him, they will have to fight, even declaring that he wants to live and be with her. Iyu is unfazed and transforms, engaging Chihiro. At first having the advantage due to her agility, she is forced out of her transformation, but still tries to fight, only to be caught by Jin, who recognizes her as Prof. Hoshino's daughter. He tells her that she has done enough and throws her aside. She then watches as Jin severely beats down Chihiro, forcing him out of his transformation. Seeing his bloodied and beaten state, she suddenly remembers what Chihiro told her during their encounter with the Sea Urchin Amazon, telling her that he would feel her pain. When Jin prepares the final blow, Iyu comes up from behind and blows apart his back, sending him tumbling down the hill. She then asks Chihiro if it hurts, much to his shock and joy. She is then reported to have fled with Chihiro by Team Amatsuki, leading Tachibana to order her extermination as well. XING THE RUBICON

The Last Hunt

Iyu and Chihiro rest at a chapel, where he hands her one of his protein packs, reminding her how to drink. As she does so, Chihiro expresses the hope that he will be able to return her to normal. Noticing a change, Iyu asks if he hurts, though he tells her he is happy. He then asks if she felt happy with her parents and sister. During the night, Tachibana activates the HS round in her Neo Amazons Register, though she feels nothing from its activation. When Chihiro is on the phone with Nagase, he hears her blood dripping to the floor, causing to panic. He tries to then fruitlessly remove the armlet, but then notices the presence of an Amazon nearby, causing him to search for it while telling her to stay. As 4C begins preparations to attack them both, surrounding the chapel, Iyu reviews her life, especially the day of her father's birthday. This causes her to remember the intense and horrifying experience she felt while her father was eating her, causing her to go berserk and attack 4C, Haruka, Chihiro and the Snake Amazon. Chihiro tries to protect her from the others, and manages to get her to calm down, forcing her out of her Crow Amazon form, though he stares in horror as she repeats how her father ate her and how much pain she was in. As Chihiro hugs her, Kurosaki orders Mizuki to fire the HS round, causing Chihiro's Amazon Origin form to surface, and produce tendrils to attack.

By the time Nagase arrives, 4C has pulled back and finds Chihiro holding Iyu, crying and asking why they are unable to live in peace. YELLOW BRICK ROAD

Chihiro and Iyu's remains: their armlets on Nanaha's shirt

After several times escaping from her pursuers with Chihiro, with her last words, she told Chihiro how happy she was and slowly closed her eyes, completely stopped functioning due to the YBR19 System. Her body was laid down by Chihiro while he fought Haruka and Jin, which he was killed offscreen.

Her body was presumably disposed by the two, with her armlet placed with Chihiro's on a shirt worn by Nanaha in the abandon park's church. AMAZONZ (season 2)

Video Game appearances

Kamen Rider Buttobasoul

Crow Amazon Medal

Iyu as Crow Amazon is a playable character in Kamen Rider Buttobasoul, alongside other Kamen Riders.


As a Sigma type Amazon, she was devoid of emotions and unable to feel physical pain, despite retaining memories while she was alive. She sports a deadpan look all the time, unconcerned if she is being treated as a person or a biological weapon, caring only about taking orders and completing assignments. Her mental faculties seem to be unaffected by her traumatic death, as she is seen fully capable of processing orders and following them to the letter. However, certain events, gestures and people relevant to her past memories can still trigger unusual reactions from her, most notable of which being singing a song her late father sang with her while she was a child, suggesting that fragments of her humanity still linger within her.

During the hunt for Chihiro after his rampage and recent discovery of him being the source behind the Amazon infections, Iyu's human side began to truly emerge upon seeing Chihiro being savagely beaten by Jin, even rescuing him when her orders were to kill him. She began showing empathy asking Chihiro if his injuries hurt.

By episode 12, her emotions finally returned in earnest after reviewing her past life, especially the night she died while celebrating her father's birthday, extensively. However, the sudden and horrifying circumstances of her death drove her over the edge in the form of a PTSD mental breakdown. Instead of merely turning human-like, the trauma turned her into a crazed killing machine, attacking and killing anything and anyone who stood in her way. However, she eventually stopped, crying as Chihiro comforted her before returning to an emotionless state.

Powers & Abilities

  • Pain immunity: As a Sigma-type Amazons, Iyu lacks the ability to feel pain. As such, she fights with a single-minded focus while sporting uncanny grace, not stopping to care about damage done to her, and will continue until her body gives out.
  • Hand-to-Hand combat: Despite having no combat experience when she was alive, she was adept at hand-to-hand combat, capable of complicated maneuvers and taking out multiple lesser foes while still suffering from wounds rendered prior.
  • Amazon tracking: Like other Amazons, Iyu has the ability to sense the presence of other Amazons. However, unlike other Amazons who detect others of their kind by scent, she detects Amazons by their urge to feed on humans. As such, while she is able to reliably detect new types as such urge is ever-present in them, she is unable to detect and identify Chihiro as one unless Chihiro feels an overwhelming urge to feed on humans.


  • Reliance on external maintenance: As a Sigma type Amazon, she is incapable of consuming nutrients and on her own, even the notion of 'eating' is alien to her. As such, she requires regular "fueling" via protein injections, else she would fail to function within a day and eventually expire. She also requires 4C to repair any damage suffered, as unlike other Amazons, she has no regenerative abilities of her own.
  • YBR19: Installed in Iyu's Neo Amazons Register, when activated this program would begin to slowly destroy her body in 5-6 hours when activated, as mentioned by Tachibana. It was implemented to dispose of Iyu in case she deviated from her original purpose.

Crow Amazon

Crow Amazon

"Amazon. (crow cawing sound)"
―Iyu transforming[src]

Unlike other Amazons and previous Sigma, Iyu needs to press the beak of her Neo Amazons Register (which turns the color of its 'eye' from blue to red), announcing "Amazon," before transforming.

Crow Amazon relies on speed and agility rather than raw power. Despite being themed as a crow, Crow Amazon doesn't seem able to fly.



Behind the Scenes


Iyu is portrayed by Ayana Shiramoto (白本 彩奈 Shiramoto Ayana), who previously portrayed Marin FumaIcon-crosswiki.png in episode 14 of Doubutsu Sentai ZyuohgerIcon-crosswiki.png.

Concept Art


  • Iyu's characteristics are similar to Mamoru/Mole Amazon.
    • Both initially act as allies of humans to hunt the Amazons.
      • Iyu is a Sigma-type Amazon working for 4C to exterminate the new-type Amazons, and Mamoru worked for the Nozama Peston Services to eliminate the test subjects.
    • Both has developed friendly relationships at least one Amazon Riders, though sometimes they will betray them due to certain reasons.
      • Iyu, as a Sigma-type Amazon, accepts orders to kill Chihiro and is otherwise apathetic because of her nature, while Mamoru grew jaded by humanity's repeated attempts to kill the original Amazons.
    • Both has saved an Amazon Rider from an another Amazon Rider by literally stabbing their back.
      • Iyu saved Chihiro from being killed by Jin, and Mamoru delivered the final blow to Jun when he attempted to flee and heal.
  • Iyu is one of the few Amazons, if any, who emits her respective animal sound when fighting. Most others only growl and roar.
  • Despite being a Sigma and both types of Drivers are available for 4C to manufacture, Iyu didn't get any, severely impairing her power compared to the first Amazon Sigma. Instead, she uses the Neo Amazons Register. Given that she is stronger than regular Amazons in the series, the Register might slightly boost her power, though not as much as a Driver could.


Icon-amazons.png Kamen Rider Amazons
Kamen Riders
Haruka Mizusawa - Jin Takayama - Jun Maehara - Chihiro - Einosuke Mido
(Neo) Amazons Driver - (Neo, Militant) Amazons Register - Junglaider
Other characters
Mizuki Mizusawa - Nanaha Izumi
Nozama Peston Service
Makoto Shido - Ryusuke Otaki - Nozomi Takai - Kazuya Misaki - Kota Fukuda - Jun Maehara - Mamoru
Nozama Pharmacy
Reika Mizusawa - Shogo Kano - Yugo Tachibana - Takaaki Tenjo
Team X
Hiroki Nagase - Kenta Kitamura - Takumi Yamashita - Chihiro
Yugo Tachibana - Shogo Kano - Takeshi Kurosaki - Ichiro Fudamori - Kota Fukuda - Iyu Hoshino - Mizuki Mizusawa
Experiment Amazonz
Spider Amazon 1 - Spider Amazon 2 - Bat Amazon 1 - Dragonfly Amazon - Mole Amazon - Queen Ant Amazon - Soldier Ant Amazon - Butterfly Amazon 1 - Butterfly Amazon 2 - Shrike Amazon 1 - Shrike Amazon 2 - Crab Amazon - Bat Amazon 2 - Wasp Amazon 1
Sigma type Amazonz
Amazon Sigma - Crow Amazon
New type Amazonz
Vulture Amazon - Panther Amazon 1 - Stag Beetle Amazon - Rhinoceros Amazon 1 - Snake Amazon 1 - Mantis Amazon 1 - Urchin Amazon - Baboon Amazon - Elephant Amazon - Weevil Amazon - Rose Amazon - Mantis Amazon 2 - Rhinoceros Amazon 2 - Panther Amazon 2 - Snake Amazon 2
Lysogenic type Amazonz
Amazon Neo - Jellyfish Amazon
Livestock Amazonz
Buffalo Amazon - Sea Snake Amazon - Shark Amazon - Snapping Turtle Amazon - Squirrel Amazon - Tiger Amazon
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