Shinji Kido/World of If

In the alternate ending, World of If, Shinji Kido (城戸 真司) was Kamen Rider Ryuki (仮面ライダー龍騎), who evolved into Kamen Rider Ryuga (仮面ライダーリュウガ) and started rampaging in the Mirror World.

Kamen Rider Ryuki: World of If
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 turn into a mindless rampant in the Mirror World. Tiger shows up and tries to stop him only to be easily defeated by Ryuga in his Survive mode.

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.

Forms
In Kamen Rider Ryuki: World of If, Shinji replaces his Ryuki Deck for Ryuga's, and as a result he goes on a mindless rampage in the Mirror World.

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

Vehicles

 * Ride Shooter - Motorcycle used by any Rider to enter the Mirror World