Months after the Hinamizawa dam incident, peace came back to Japan. Everything was basically back to normal, no monsters anymore, however one day, a girl by the name of Kagami Hiiragi began to have weird dreams of an unknown kamen rider. The latest dream is that she was standing on a grassy field, before later an entire army of riders, alongside their leaders Kuuga, Agito, Ryuki, Faiz, Blade, Hibiki, Kabuto, Den-O, and Kiva charging on the unknown kamen rider. However they were all destroyed in one attack. In that dream though, she has one clue.

The name of the rider is Kamen Rider Decade, destroyer of worlds.

"That same dream again..." Kagami said waking up.

She then looked to see Tsukasa, her younger twin, staring out the window.

"Hey Tsukasa, what are you daydreaming now?"

"I think there are different versions of worlds, Onee-Chan." She replied.

"Ahaha, don't daydream nonsensical things, Tsukasa! You're already 17!" Kagami said, before seeing something at the window.

A square shaped device, and a strange book made of silver.

'Those things... Were in my dreams!' Kagami thought, her eyes widened.

"Hey Tsukasa, where did you get those 2?"

"Oh these? They suddenly popped up after I woke up this morning." Hearing that shocked Kagami, She then took the 2 strange objects, wanted to show them to Konata, her best friend.

Half an hour later, they arrived at school and went to class, and met Konata, sitting on her desk.

"Hey Konata!"

"Oh, Kagamin~! What's up?" She greeted back.

"Do you seem to know what these things are connected to?" Kagami said, showing the 2 objects to Konata.

"W-Well, They suddenly appeared when i woke up this morning, Kona-Chan." Tsukasa explained further.

Konata then inspected the object, and saw that there were 9 rider symbols, which were familiar to Konata.

"This is a transformation device, if i could say, and this book here, it's a holder for the transformation components." Konata explained.

-Later, after school...

Kagami still held the objects, and walked home with Tsukasa, however suddenly a white barrier appears, separating the twins.

"Onee-Chan!"

"Tsukasa!"

However then Tsukasa's eyes widened as she saw another Kagami behind Kagami.

The other Kagami then glowed in a green light, and morphed into a monster with a large shell at the left arm, forming a shield, while the right arm has a claw.

"KYAAA!" Kagami shrieked.

"Onee-Chan, give me those devices! Trust me!" Tsukasa said, seeing that the devices can go through the barrier.

Kagami at first hesitated, however seconds later, She gave them to Tsukasa.

Kagami then tried to defend herself using her school satchel, while Tsukasa puts the square device to her waist, which then fastened automatically around her waist, forming a belt.

"NO!" Kagami screamed, as the worm continued to get close to her.

Tsukasa hurriedly opened the book, and took something, a card with the words Kamen Ride Decade, and a picture of said rider. Tsukasa then held the card with her left hand, and rotated the belt buckle 90 degrees.

"Henshin!" However She then realized that the card is at the wrong position, and flipped it.

"Henshin!" She said again, inserting the card to the slot.

"KAMEN RIDE" A robotic voice said.

She then rotated the buckle back to the original position.

"DECADE" The voice said again.

Multiple silhouettes appear near Tsukasa, and merged with her, transforming her into Decade.

The barrier then shattered into pieces upon Tsukasa's transformation is complete. The shattered parts hit the monster in the back, making it flinch and turned to face Tsukasa.

The monster suddenly moved in high speed, which made Tsukasa unconsciously picked a card from the card book, it has the name "Kamen Ride Kabuto". She then inserted the card into the belt buckle, which she rotated 90 degrees.

"Kamen Ride..."

She then twisted the belt back to the original position.

"KABUTO"

Nano waves then covered Tsukasa's body, changing her from Decade to Kabuto.

She then unconsciously again took a card with the label Clock Up and an image of Kabuto sidestepping, with afterimages, before inserting it to the belt buckle just like before.

"ATTACK RIDE, CLOCK UP" Tsukasa then moved in the speed of light, and beat up the monster into submission, causing it to explode.

However, after that She returned into Decade.

"Why did I used this card?" She asked herself curiously.

Suddenly the card turned grey.

"Tsukasa!" Kagami called out.

"Onee-Chan! Let's get out of here!" Tsukasa said, running with Kagami to Konata's house, where her friends, Konata and Miyuki included, were waiting.

"Ah, quickly, come in, Kagamin! Tsukasa!" Konata said, opening the door halfway.

Once inside, they began to discuss.

"Looks like things had gotten more worse. Worlds beginning to collide." Miyuki explained.

"But that's lucky Konata-Nee has something!" Yutaka said

"What is that?" Tsukasa asked.

"This! Dimension warp, Kuuga!" Konata replied, holding a wallpaper depicting a town from the anime Yu Yu Hakusho.

Then a bright light sparkled from the wallpaper.

Once Tsukasa had realized, she was outside Konata's house, and that She was riding a bicycle.

"Eh? What?"

"Units report, an unknown creature had just appeared in a... Umm... The commercial district." A voice came out from a cop radio.

To Tsukasa's surprise, she was wearing a police officer uniform, and that the radio sound was from the radio that was attached to the uniform.

Tsukasa then cycled her way to the commercial district, and saw someone.

"Henshin!" The man said, doing Kuuga's transformation pose.

A beeping voice then came out from the man's belt, before transforming him into Kuuga.

"The world of Kuuga!?" Tsukasa asked in disbelief.

-To be continued

A/N Well, this crossover fic will be the largest in my opinion. Here are the riders and the people who will become them.

Kuuga- Yusuke Urameshi (from Yu Yu Hakusho)

Agito- Haruhi Suzumiya

G3X- Kyon

G4- Ryoko Asakura

Ryuki- Nueno Meisuke (from Jigoku Sensei Nube)

Ryuga-???

Faiz/555- Akihisa Yoshii (from Baka Test)

Orga- Yuuji (alongside Akihisa)

Blade- Clifford D. Lewis (from Eyeshield 21)

Glaive-???

Hibiki- Ginnosuke Nohara (both old/young)

Kabuki- ???

Kabuto- Yuuya Kizami

TheBee- Ryosuke Katayama

Drake- Kai Shimada

Gattack- Kensuke Kurosaki

Kick Hopper- Imitation Mion Sonozaki

Punch Hopper- Imitation Shion Sonozaki

Caucasus- ???(summoned by DiEnd)

Dark Kabuto- Shinnosuke Nohara

Den-O- Hiruma Yoichī (from Eyeshield 21)

Kiva- Satoshi Mochida (child)

Arc- Yoshiki Kishinuma (child)

DiEnd- Konata Izumi

I hope you enjoy this crossover and leave a review! Cya!

-By YuuyaKizami21, A just passing through User