I decided not to go with Yoshikage Kira because of two reasons.

1, I feel like he'd be OP, even with the nerfing I give him. 
2, I found someone who is a better fit for this RPG.

Name: Alain

Universe: Kamen Rider Ghost 

Appearance: http://i.imgur.com/1rMBwXr.png

Personality: He is pretty cold and calculative, but also temperamental and doesn't tolerate failures. He also doesn't tolerate insubordination, treason, or people responding to people with a higher power than him. He believes that indivisual lives have no value and that the Ganma world is his ideal world. He also has an almost yandere feeling towards his friends. Those whose friendship makes his friends turn sides will get his full wrath, as Takeru had found out when Makoto switched sides. Because of his Ganma nature, he is unaware of tons of human concepts, like hunger, grief, thantophobia, love, friendship... the list goes on.

Abilities: Alain's body is actually an illusion. His true form is a small object called an Eyecon. If the 'body' takes enough damage, it is destroyed and the Eyecon is destroyed with it, sending Alain's soul back to a pod in the Ganma World where his body resides. Since this will take him out of the conflict, this, at least as far as the RPG goes, will be treated as a death.

To make up for this though, Alain has a device called a Mega Uloader, which, with the Necrom Eyecon, allows him to become Kamen Rider Necrom. The armor he has is made out of Quantum Liquid, which allows him to liquefy and phase attacks like a ghost, but also to form the liquid as tentacles for attacking and grabbing. The drawback is using this liquid quickly drains the energy for Necrom and once it gets drained to nothing, the Necrom Eyecon must recharge.

To counter this, Alain subjugated two Heroic Eyecons to act as temporary placeholders in case this happens. One is the Eyecon of the Brothers Grimm, who give him the ability to use a tentacle-like dagger called the G Pen, and Sanzo,  who gives him a large ring for fighting and also the ability to summon a getaway cloud made from Wukong, Bajie, and Wujing. 

Alliance: Team Zuriel

Other: This is right after the whole Necrom!Specter fiasco. 

Will this suffice?