Alright first off
NO KNOWLEDGE OF KAMEN RIDER NEEDED! I will explain everything you need to know in the sections below. Its' a Japanese superhero show but it will probably be enjoyable for anime and manga fans as well (as Kamen Rider was created by Shotaro Ishinomori, creator of Cyborg 009 and a popular manga writer). Now, why don't you need prior knowledge? Because each Kamen Rider series is a self contained story, most having no connection to previous series, so if you know the basics, you'll be perfectly fine.
Plot: In ancient Japan, a race of beings called the Akuma (translates to demon or devil), supernatural creatures whose origin is unknown even to this day, ravaged ancient Japan. However, an ancient samurai rose up and challenged these evil beasts, fighting valantly against their evil. But he alone was not strong enough to overcome them all and seeing his power, the monsters attempted to convert him to one of their own, that is until a miracle took place. Some say the spirits above intervened in his favor, other say his heart was simply too pure to be twisted into their evil ways. Reguardless, their attempt backfired and instead of gaining a powerful new ally, they gained an enemy they couldn't overcome. The samurai turned into an armored warrior known as Kamen Rider Kage. With his great power he overwelmed their foces and finally impaled the Akuma King on his own sword, causing all the Akuma to be sealed within it, which Kage trust into the depths of the sea so they'd never again harm the world of man. With his quest completed, Kage vanished into the shadows.
In modern day Japan, the exploits of Kage are believed to be little more than a legend. But that legend soon becomes frightenly real when the sword containing the Akuma King is dredged up from the ocean's depths. As its examined, the seal is broken and the legions of monsters were unleashed once more. Quickly setting up their ancient base in the heart of Mt. Fuji, the Akuma King sends his menions to unleash destruction on the world of man. However, fate would once again conspire against the monsters, as the descendent of Kage regains his ancestors power, but is still learning to use it. With the new Kamen Rider Kage fighting back, the Akuma King commands his menions to hunt down and murder the descendents of Kage, so another such warrior can't rise against them. But some of them awaken despite this and continue their battle with the evil Akuma.
Rules:
No killing someone without permission. Akuma can be killed but you have to fight them for a period of time first.
No 'god powered' characters.
No God Mod or Powerplay.
Be kind to other roleplayers.
Not everyone has to be a Kamen Rider or Akuma, you can be a normal human trying to help.
Have fun!
Kamen Riders: Kamen Riders are Japanese armored superheroes that ride motorcycles and fight Kaijin, humanoid, human sized monsters. That's litterally the only things they all have in common. Most can also do a Rider Kick, a powerful flying kick used to finish the monster off, but some don't have one, however, all of them have some form of finishing move. They normally have an animal base for their armor, for example this Rider, Kabuto, is based off a Rhinoceros beetle:

In this RP, Kamen Riders transform with a belt mounted device that materilizes when they want to transform. In its middle it has a crystal resembling an eye, its closed at first but when the Rider says "Henshin!" (Japanese for transform or transformation), it opens up and they transform. If the Rider has a weapon, it materilizes out of this eye. When they begin to awaken as a Kamen Rider, their bodies get physically stronger and they subconsciously gain combat knowledge as their body prepares them for the transformation.
Akuma: The Akuma are ancient spirit beasts that resemble humanoid animals in samurai-like armor. Each one has an elemental ability based on one of the five Japanese classical elements: Earth, Fire, Wind, Water, Void (meaning things humans can't understand). Only Mao, the Azuma King, has the Void element and can also use the other five. Normal Akuma normally aren't addressed by name, but higher ranking ones are. Most of them will serve a 'villain of the week' role, appearing to cause destruction and fight the Riders. When killed an Akuma's body cracks, causing their elemental energies to leak out before they explode. Akuma do have a code of armor, requiring that if they lose their will to fight to destroy themselves, if they don't then another Azuma must.
Bios:
Rider Bios: (IF you want a normal human, leave the Rider related stuff blank)
Name:
Rider Name:
Age:
Personality:
History:
Animal Base:
Armor Appearence:
Weapons:
Catchphrase: (what they say ether at the begining of the battle or before preparing their finisher)
Finishing Moves: (create three, can be anything, though one is encourged to be a kick of some kind)
Akuma:
Name:
Age:
Personality:
History:
Animal Base:
Element:
Weapons:
Name: Jarret Hikari
Rider Name: Kamen Rider Kage
Age: 20
Personality: Kind, friendly, somewhat naive at times but in battle gets serious and focused.
History: He was a normal boy, living in Japan with his parents. However, when the Akuma awakened, he began to change, becoming stronger. Finally, when an Akuma killed his family, he transformed into Kamen Rider Kage to fight them. Since then, he's been facing the Akuma to stop their evil.
Animal Base: Rhinoceros Beetle.
Armor Appearence: Its a dark reddish brown and streamlined, fitting his body. Its shoulders, arms, chest, and legs are heavily armored, a flexiable but durable fabric between the armored plates. His helmet has two large red-beetle-like eyes and a single horn like a Rhinoceros Beetle. The eye in his belt is green
Weapons: Terra Shredder: A samurai sword pulled from his belt. It's hilt has a large green crystal in it and the hilt seems to have one side oversized. This part, however, can be folded up to transform the sword into an ax.
Catchphrase: "Those who do evil will feel my blade!"
Finishing Moves:
Purity's Light: His right foot glows with a radiant light before he jumpped into the air and lands an ax kick on the target's head.
Assault Blade: Runs his hand over the jewel on the Terra Shredder while in sword mode, causing the blade to glow. He then charges the opponent and delievers a series of fast slashes. He also perform this move by simply slashing in front of him, sending an energy slash through the target.
Terra Crusher: Runs his hand over Terra Shredder's jewel while in ax mode, then charges the opponent and slashes with one hand, the ax getting caught in their shoulder before he grabs it with both hands and finishes the slash.
Name: King Mao
Age: Several centuries old.
Personality: Cruel, sadistic, evil, hats those who will dishonor themselves. Craves a worthy opponent.
History: The kind of the Azuma, he ravaged Japan in ancient times, until the original Kage appeared. After an epic battle, he was impaled on his own sword, imprisoning him and the rest of his kind inside it. Released into modern Japan, he seeks to continue he age old rampage. He still bares a glowing scar in his chest from being impaled by Kage.
Animal Base: Elepant Beetle.
Element: Void, all other elements.
Weapons: Muramasa Blade: A long katana forged by the legendary swordsman it's name implied. It an evil blade that compales the user to commit acts of terrible bloodlust. Only one with a pure soul, good or evil, can wield it without this effect. It is too heavy for a normal human to lift as it is. Only two beings are known to have weilded it without sucumbing to its curse, King Mao, and the original Kage. If King Mao is impaled on it, he and all the Azuma will be imprisoned within it.