Dark Shinji/Zi-O

In 2002, Dark Shinji was Kamen Rider Ryuga (仮面ライダーリュウガ). Seventeen years later, he becomes Another Ryuga (アナザーリュウガ), created by Heure and Sworz.

In Rider Time: Kamen Rider Ryuki, he becomes Kamen Rider Ryuga again in order to participate in the new Rider War, serving as one of the primary antagonists.

Mirror World 2019
Heure was able to meet Dark Shinji thanks to Tsukasa's information about "that" another world. Heure learned that Dark Shinji had once been defeated in a Rider War, but as long as the real Shinji Kido exists, Dark Shinji will continue to manifest. Thus, Heure gave him the Ryuga Another Ridewatch, enabling him to transform into an Another Rider.

Sougo and Geiz try to defeat the Another Rider but to no avail, as all the attacks they dealt were reflected back. Geiz searched for White Woz to ask for assistance to take him down, only to have White Woz attack the real Shinji instead, as he stated that if Shinji is gone then so will Dark Shinji. This made Dark Shinji fight against White Woz and he reveals himself as Another Ryuga, and proved to be far too strong even for White Woz. Even Woz Futuring Quiz's ability had stated that Another Ryuga can't be defeated.

After Another Ryuga's will to fight went down, he returns to the Mirror World, but Sougo tried pulling him back, which resulting in Sougo being dragged into the Mirror World as well.

Zi-O Strongest! 2019
Another Ryuga keeps hunting the past clients of ORE Journal, defeating both Geiz and White Woz again in the process. Despite Geiz's suicide attack, Another Ryuga is not defeated. After Sougo appears as Kamen Rider Zi-O II, Another Ryuga is destroyed for good. Sougo then advises Dark Shinji to accept the real Shinji, just as Sougo has just accepted Mirror Sougo earlier.

In the end, Dark Shinji's fate is left unknown. Though he will continue to exist no matter what, Shinji's reflection does return shortly after, meaning that Dark Shinji might have accepted his real counterpart.

Another Alternative
In 2019, a mysterious person restarts the first Rider War in the Mirror World. Dark Shinji first appears in Shinji's dream when the latter is knocked unconscious by Zolda's Final Vent, talking about letting them unite once more, much to Shinji's horror. Dark Shinji then appears to explain Shibaura's scheme to Tezuka, which leads them to fight each other.

After Tezuka's demise, Dark Shinji reappears and succeeds in taking over Shinji's body yet again. Afterward, he meets Jun Shibaura, proclaiming that Tezuka is dead, and he'll 'Love' him in his place, before transforming into Ryuga. Ryuga easily defeats Gai with his Final Vent, and stomps on Jun's body as the latter disintegrates.

Alive A Life
After witnessing the death of Jun Shibaura at the hands of Dark Shinji, Kimura and Ren are shocked. Ryuga then attacks Kimura, wanting Kimura to die for him, saying that if he wins the Rider War, he can escape to the real world and exist as a real being. Ren transforms into Kamen Rider Knight and uses Trick Vent to distract Ryuga. Ryuga swiftly defeats the Trick Vent copies, only to find out Ren and Kimura have already escaped.

Dark Shinji comes and offers to "play" with a vexed Asakura. Finally happy with a chance to fight, Asakura transforms and charges at Dark Shinji. The two fights a brief while before Knight, who has regained his memory,  appears and strikes Ouja, remarking that Kido's opponent is not the madman but him. Ouja is amused and begins fighting Knight. Knight tells Ouja that he is merely wanting to die, then uses his Final Vent on him right after, fatally wounding Ouja, forcing him to flee. Knight then attempts to take on Ryuga alone. Ren tries to make Shinji remember the past, and reveals to him that the voice inside his head is Shinji's, which keeps telling him to stop the war. Nevertheless, Dark Shinji states it is useless to try and bring his real counterpart back, as he no longer exists. Ren shouts at him, telling Shinji to come back, otherwise, he would have to kill Shinji. The two transform and begin a duel, with Ryuga being the winner.

As Ryuga is about to land the killing blow on Knight, the real Shinji begins to surface and forces Ryuga to stop the attack. Ren says that Dark Shinji can never win because he does not understand the bond between him and the real Shinji. Knight then strikes Ryuga, forcing him back into human form. Ren, thinking that Shinji has returned to normal, de-transforms and comes by his side. However, Dark Shinji is still in control of the body, he grabs his Black Drag Saber and fights Ren in human form. The fight is interrupted by an Asakura, also untransformed, wielding his Veno Saber. As Asakura prepares to kill Shinji, Ren shields him from the blow and receives a fatal wound as a result.

It is at this point that Shinji manages to remember his past and uses his willpower to subdue Dark Shinji. This time, both Shinji seem to coexist in unison as Shinji continues with his life; thus, Dark Shinji's wish to become real along with accepting the real Shinji come to a close.

Personality
In Zi-O, he returns as a manifestation of Shinji's rejected dark heart but still has his old persona during the events of Ryuki. Therefore, after becoming Another Ryuga, he targets the readers of ORE Journal who Shinji secretly blamed for the closure of the magazine.

Powers and Abilities

 * Mirrored Human Physiology
 * Immortality: According to Huere, as long as the real Shinji Kido is alive he cannot be defeated. He is shown to be alive even after his defeat by Shinji when their Final Vents collided.
 * Doppelgänger Morphing: Dark Shinji can take the appearance of other beings.

Weaknesses

 * Real World: Creatures from the Mirror World cannot exist in the real world for too long without being disintegrated. This also means that if he ever continues to exist outside of the Mirror World, his powers will be weakened significantly.
 * Shinji Kido: If Shinji Kido is killed, Dark Shinji would cease to exist as well. White Woz predicted that this can even override the invulnerability of the Another Rider. However, Heure suggested that doing so won't work. Although, Dark Shinji is finally subdued for good by Shinji willpower alone, after all, they are both two sides of the same coin.

Equipment

 * Advent Deck - Transformation device and Advent Card holder
 * V-Buckle - Transformation belt
 * Advent Cards - Trinkets that enable a Rider to summon Contract Monsters, access equipment, and use special abilities
 * Black Drag Visor - Ryuga's Visor that enables him to use Advent Cards
 * Anotherwatch: Another Ryuga Transformation device

Portrayal
Mirror Image Shinji Kido is portrayed by Takamasa Suga (須賀 貴匡), who also portrayed the lead role of Shinji Kido. As Another Ryuga his suit actor was Kazuya Okada (岡田 和也).

Appearances

 * Icon-zi-o.png Kamen Rider Zi-O
 * Episode 21: Mirror World 2019
 * Episode 22: Zi-O Strongest! 2019
 * Part 2: Rider Time Ryuki
 * Episode 2: Another Alternative
 * Episode 3: Alive A Life