Kamen Rider Ryuki: Episode Loud: A Kamen Rider Ryuki and Loud House Crossover: Prologue Part 1.

Shiro Kanzaki: a man with an obsession with saving his sister from death that would occur when she would turn twenty. Shinji Kido, better known as Kamen Rider Ryuki has gotten in his way, too many times. Shinji has but one goal: to stop the other Kamen Riders from killing each other and to protect the people from Mirror Monsters: monsters created by Shiro's cousin Yui. These monster feed on other humans to survive on their lifeforce. There are two types of monsters: The contract monsters and the regular monsters that feed on humans. The contract monsters are monsters that are contracted to the Kamen Riders. The regular monsters abduct people so that the monsters can feed. Long ago, Shinji Kido discovered an Advent Card deck and soon after being sucked into the mirror worlds, meeting Kamen Rider Knight: Ren Akiyama, and contracting Dragreder, a dragon-like monster, Shinji enters the Rider War to save people from the Mirror World and stop the fighting between the Kamen Riders as Kamen Rider Ryuki. Shiro has had enough of Shinji trying to thwart his plan to reunite with his sister, Yui. So this time, he contacts the four remaining riders: Ryuki, Knight, Ouja, the new rider, Femme, and Zolda, one at a time. First, he contacts Shinji Kido, Kamen Rider Ryuki, at his house, through a mirror.

"What do you want, this time" Shinji asked?

"I am moving the Rider War away from here" Shiro said.

"What" Shinji exclaimed!?

"I am taking the Rider War and I am moving it away from Japan" Shiro said. "I am moving it to a different place".

"What different place would that be" Shinji asked?

"That place would be Royal Woods, Michigan" Shiro answered.

"Michigan" Shinji asked? "But that's in the United States of America".

"Exactly" Shiro said, "which is why I will be stowing away onto a plane in the mirror world".

"But there is no one in the mirror world who can fly a plane" Shinji countered.

"It's a private plane I am stowing away on" Shiro said. "I will be on Shuichi Kitaoka's plane".

Shinji gasped. Shuichi Kitaoka was the fourth Kamen Rider and a lawyer who prefers to do stuff for his own gain. How was Kitaoka able to get a private plane?

"Don't bother meeting me there" Shiro said. "I don't think you will get on Kitaoka's plane just by asking". "This is one chance you won't get to stop this war".

"We'll see about that" Shinji said angrilly.

"If you want to get to Royal Woods on time, be at the plane by 7:00 AM" Shiro said. "Otherwise, there is no way you can stop this war".

"I'll get to Kitaoka's plane and I will prevent the war from killing innocent people in Royal Woods" Shinji declared.

"Very well" Shiro said after a long moment.

Meanwhile, Kamen Rider Ouja: Takeshi Asakura and Kamen Rider Zolda: Shuichi Kitaoka were battling in an abandoned warehouse in the mirror world using their punches and kicks. They then drew one card each out of their advent decks.

"As of today, your existence alone has vexed me" Asakura said angrilly.

"Still going on about being vexed, eh" Kitaoka asked?

Kitaoka's card read "Shoot Vent". He grabbed his Magna Visor, a gun/pistol shaped weapon which is his default weapon, put the card in the slot, and pushed the slot into the weapon.

"SHOOT VENT"

At the same time, Asakura put his "Unite Vent" card in the slot and pushed the slot into his Veno Visor, a scepter-like weapon of his.

"UNITE VENT"