Yui Kanzaki

Yui Kanzaki (神崎 優衣, Kanzaki Yui) is a main character in Kamen Rider Ryuki. She is the sister of Shiro Kanzaki, the creator of the Decks, and she, with Shiro, is the partial creator of the Mirror World and it's Mirror Monsters. She spent most of the series opposing her brother on the Rider War.

Personality
Yui at heart is a young innocent girl who is caring to anyone she meets. However, this trait is what causes her the most trouble as a majority of the people around her are associates of the Rider War and only wish to use her to their advantage.

She hates fighting, as shown by the multiple times that she attempted to stop Shinji and Ren from fighting each other.

History
Yui originally lived with her grandmother, but when her grandmother went overseas, she met Ren somehow, although how this occurred is not specified in the series. Coincidentally, Ren was a Kamen Rider who had received his deck from Shiro at some point in time in Japan. Yui became somewhat of Ren's accomplice and would accompany him to fights where he would enter Mirror World and fight.

Time passed and eventually she also met Shinji, who would became Kamen Rider Ryuki. Her grandmother returned from her overseas trip and she began to help out at the cafe that her grandmother owned. She was kidnapped by Kamen Rider Scissors to use as bait to lure out Shiro but Ren was able to rescue her before that happened. Later, she went to Seimeiin University to inquire about her brother but everyone she asks was much less then helpful. After finding her brother in a Yearbook, Her past; which she previously had no memory of, began to reveal itself to her and she met Professor Ejima who worked alongside Shiro during the development of the decks. Ejima died in her arms but not before he told her that everything would have been fine if she had never existed.

She gets a part-time job at ORE Journal while the Chief-Editor recovers.

After continually bothering Nakamura about her brother, he eventually gives in and provides her with a number of papers about Shiro. She learns about a Woman named Eri (who coincidentally again is Ren's fiancée) who is in a coma at the hospital.

She is eventually kidnapped by Jun who uses her as bait to lure out Shinji and Ren into battle. Eventually, she manages to find a picture of her old house and goes with Tezuka to have a look but can't bring herself to go in.

Throughout the series, her past continues to unravel even further, she learns many things about her childhood, including that the drawings she and Shiro had created as children were the basis for the Mirror World's monsters. She and Shiro had had neglectful parents who kept them locked up in the attic for long periods of time, and when Yui fell ill, she and Shiro could not get their parents' attention. When she, the original Yui, died, the Yui of the Mirror World (as Shiro and Yui had also drawn themselves) asked to inhabit her body so she could live in the real world. Shiro, wanting his sister back by any means, allowed it. The Yui of the series is this mirror version, and had forgotten.

The Mirror Yui had told Shiro that on her twentieth birthday, she would cease to exist along with the original Yui's body. The purpose of the Rider War was to prevent this from happening.

Yui begins to fade, just as predicted, as she nears her 20th birthday. Even though Shinji, Ren, and Shiro do all that they can to save her, she fades away even though the deadline had not quite been reached. She later appears to Shiro, appealing him to stop his destructive course of actions, saying that to be saved in that manner was not what she wanted, and that she would rather make the mirror world a happy place that would not cause suffering. Shiro agreed, and there is a scene in which she and Shiro, alongside their child selves, draw together, but this time, with happy scenes instead of monsters.

The scene makes no literal sense, but it is believed that Shiro used the power behind Time Vent (even though Odin was fighting Ren at the time) in order to alter history so that the Mirror World was never dangerous and the Rider War never happened. In the new timeline that results from this, there are no Mirror Monsters or Kamen Riders, and all those harmed by the Mirror World are seen to be living normal lives. However, when Ren and Shinji meet the Kanzakis' grandmother, she is alone and the only picture of Yui is as a child. As such, it would seem that in the new timeline, Yui's death as a child was not prevented, and Mirror Yui never took her place.

Episode Final
In this alternate story, Yui and Shinji already met each other as a child as they promised each other to play again in the next day. But however, it didn't turn out well as Shinji didn't came out due to rain as she return home. Saddened of what happens to her, Yui's mirror counterpart pays her a visit and accompany her to play in the Mirror World. However things only getting worse as she will die when return. The mirror counterpart agrees to lend Yui her lifespan which will only last on her 20th birthday in an exchange for her drawings of the Mirror Monsters. Before returning, she visit Shinji (via mirror transportation) and plays with him for the last time.

In the present day, she locks herself in an abandoned room at an apartment with Shiro appears and celebrate her 20th birthday. When Yui finally dies, Shiro screams out of his failure and vanishes as the battle of Knight and Ryuga continues, they crashed into Yui's room, with Knight transforming back into Ren and devastated with Yui's death. As Ryuga is about to finish him, he witness Yui's corpse and with Shinji (who was earlier duped by Ryuga himself) finally escapes as he realized that Yui never wanted anybody's life and rather leave herself dead giving Shinji/Ryuki a higher hope to defeat Ryuga.

S.I.C. Hero Saga
Yui appears in two S.I.C. Hero Saga which is Kamen Rider Ryuki: Advent Calendar and in Kamen Rider Ryuki: World of If.

With the Rider War is reaching it's final, Ryuki, Knight, Ouja, Zolda and Odin are the surviving Riders left. While Ouja fought Knight he causes Knight to buried under some rubble. Ryuki shows up and challenges Ouja into a fight as he stole Knight's Survive Card and and transformed into Ouja Survive with Venosnaker evolves into Venoviper. With Yui just happened to be nearby, Ouja summons Venoviper while holding Yui as it's hostage. He then uses his new Unite Vent card with all the contracted monsters' cards he's gathered up till now from the Riders he defeated with Darkwing card which he also stole from Knight. All of his monsters, as well as Dragredder which just happened to be nearby, combine to form the Genosurvivor. However, Dragredder still belongs to Ryuki and its head starts snapping at Venoviper's (Venosnaker's Survive form) head. With the combination of Genosurvivor starts to ran out of control, it tries to attack and destroy the Mirror World.

Kitaoka shows up saying that he knew something weird was going on in the Mirror World because he was in his car when it's windscreen just cracked. He transforms into Zolda and summons Magnugiga and uses End of World, blowing everything away. Ryuki sees the rubble with Knight in it blown away too and with his love, anger and all of his sorrow his body possessed by the spirit of his late order brother, Shinichi Kido. Looking at the dead body of Ouja and Zolda (who also died after caught in the explosion of his own attack), Yui says he did it, and when doing so he and Dragredder had turned black means that now he is Ryuga.

In this S.I.C. alternate retelling of the story, the remaining Riders are Ryuki (now Ryuga), Knight, Tiger, Ouja and Odin.

After Shinji becomes Ryuga, he starts to rampaging on the Mirror World. Hideyuki Kagawa, as Alternative Zero shows up with an army of twelve Alternatives in order to destroy Ryuga. As they prepare to attack Ryuga, Yui Kanzaki shows up. Kagawa laughs; Yui is the source of all their troubles and if she dies everything will end. They attack her instead, but Ryuga, having his sanity returned shields her. He reverts to Shinji and dies. Kagawa is shocked that there's a Kamen Rider who would give up their life for someone. Yui says she has a favour to ask of him.

With the Survive Card in his hand, Ouja, as the final Rider, stands before Odin. While in the middle of the battle, Alternative Zero jumps in and join forces with Ouja in order to fight Odin. Ouja activates his Final Vent; Venoviper transforms into a bike and charges at Odin, spitting poison along the way. A moment before it hits him, though, he activates his Time Vent and vanishes, then reappears on Venoviper's seat, behind Ouja and strikes him quickly.

Right before he dies, Asakura sees Odin's face, through the hole in his helmet melted through by Venoviper's poison, revealing Ren's face. The mask completely crumbles away and Ren comes back to his senses. He looks down at his body and realized what happened. After Eri died, he quits being a Kamen Rider while throwing away Knight's Advent Deck. While wandering at the streets, a man shows up and give him an Advent Deck and turned him into Odin's puppet.

With a full anger, he yells by the name of Shiro Kanzaki as he appears and laughing in glee. Now that Odin is the victor of the Rider Battle, and now he can finally grant Yui a new life. Ren notices that the Alternative Zero and has a weird feeling about him as he heads over and yanks out the deck. Turns out it was Yui all along. She revealed that she borrowed it from Kagawa to stop Shirou, and reaches out to him. But he has no body, and can't grasp her hand. Yui faints while dies as Shiro failed to grant her a new life and mourning her death.

Rider Statistics
In the S.I.C. Hero Saga, Yui became the Alternative Zero in order to confront Odin. The Alternative Deck gives her these following stats. Ability Perimeters
 * Height: 190cm
 * Weight: 93kg
 * Maximum Running Speed: 100m/4.5s
 * Sight: 20km
 * Hearing: 15km
 * Maximum Jump Height: 50m
 * Punching Power: 300AP
 * Kicking Power: 450AP

Contract Monster
The Alternatives' sole contract monster, Psycorogue, resembling a humanoid cricket, Psycorogue could transform into a motorcycle called the Psycoroader. This contract monster has white armor with black accents while Alternative Zero and Alternative's armor were black with white accents, contrary to other Riders whose armor was similar with their contract monster. Its name is a portmanteau of the two words, psycho and koorogi, which is cricket in Japanese. The Final Vent Dead End transforms Psycorogue into a motorcycle then Alternative and motorcycle spin-out faster and faster until they ram into the opponent.

Advent Cards
Unlike the other Advent Cards, Alternative and Alternative Zero's cards are different in appearance; the terminals and images are printed crosswise unlike the original Advent cards that have theirs printed lengthwise, and are given the title, "Alternative Advent Card Alchemy System" at the back. Also, there are green characters on the cards, which may give information to the Visor on what kind of card is swiped. Because their equipment was designed by themselves, the V-Buckles' and Card Decks' appearances were different from the other Riders.

Slash Visor: The card reader of Alternative Zero/Alternative was mounted on his right forearm. The visor voice was different from those of real Riders, the voice was female. Another difference was how the cards were used with the visor. The cards were swiped (similar to the rouzers which would later be used in Kamen Rider Blade), which burned up with jet-black flame and disappeared when the card was vented.
 * Advent (AP: 6500): Summons Psycorogue.
 * Sword Vent (AP: 2000): Conjures a lance.
 * Accele Vent (AP: 2500): Increases Alternative's movement speed.
 * Wheel Vent (AP: 4500): Transforms Psycorogue into Psycoroader
 * Final Vent (AP: 8000): Executes Dead End. Psycorogue transforms into a motorcycle, then Alternative and motorcycle spin-out faster and faster until they ram into the opponent. Only Alternative Zero performed his Final Vent. Alternative was killed before performing it.

Portrayal
Yui Kanzaki is portrayed by Ayano Sugiyama (杉山 彩乃).