AU Bio: This AU cluster brings a mix to Youkai Watch and Kamen Rider, specifically Kamen Rider W/Fuuto PI and Kamen Rider Ghost. There is the KM Triple AU, with Keita becoming a Kamen Rider with Whisper and Jibanyan, the Fuuto PI Teamup AU, where the Dopants begin becoming Kaima and the Narumi Tanteisha are joined by 41-year-old Keita who never lost his memories/11-year-old Keita, the Fuuto PI Future AU, where the Narumi Detective Agency is called to Y Gakuen to help find out the truth about Kirameki Sasuga and co while also dealing with Onryo, and the Youkai Rider Enma AU, where Itsuki and Shien replace Shotaro and Philip respectively.

Kamen Rider Triple AU

Amano Keita is just a normal kid who gets involved with Youkai when his computer spits out a spectral butler named Whisper and a thing called the Enma Driver. Contracted to him and a lazy Nekomata named Jibanyan, Keita finds himself fighting against Onryo, humans that have been given Youkai Medals to insert into their bodies in order to gain their power. Thus begins the saga of Kamen Rider Triple in his journey to save Youkai from humanity's greed. Later on, Whisper and Jibanyan, plus the other Youkai return to the Youkai World following the defeat of 3 villains, only to come back some years later just in time to deal with a new organization. He and his friend, Misora Inaho/Kamen Rider Vader, end up meeting an amnesiac person named Kirameki Sasuga, who can become Kamen Rider Beast and was soon discovered to be from a different timeline. Following the fight against the organisation, Sasuga regains his memories and returns to his timeline (Fuuto PI Future), saying goodbye to the two before leaving. 

Fuuto PI Teamup (Shadowside AU)

The Narumi Detective Agency is approached by a new client, but soon they realise this case is different; the culprit is neither visible nor tangible. They are unable to fight against this new force until a mysterious Kamen Rider comes into the scene. Known only as Shadow, Philip soon finds out about the Youkai species and they find Keita. They team up to defeat Onryo, the Youkai equivalent to Dopants, with new Drivers called the Yin-Yang Driver and new Memories. Philip gets Light, while Shotaro gets Shadow (the one Keita had owned before). Keita gains new Memories thanks to his friend, Shutendouji, who is searching for a girl named the Princess, who turns out to be his own daughter, Natsume. The team then has to fight off Soranaki, a Shinma Youkai who plots revenge against Natsume's incarnation, the Oni Queen Shuka. 

Philip - Light, Omamori, Tsukumono, Izana

Shotaro - Shadow, Shinma, Kaima, Uwanosora

Ryu - Onnen, Goriki, Mononoke

Keita - Oni, Mikakunin, Onimaro

Tokime - Mikado

Fuuto PI Teamup (OG AU)

Similar to the Fuuto PI Teamup (Shadowside AU), but with Keita being Kamen Rider Enma instead, while Shotaro and Philip get different Gaia Memories based on the Tribes while they face time traveling shenanigans against an insane Youkai named Nura (my OC).

Philip - Pretty, Pokapoka, Fushigi

Shotaro - Isamashi, Usurakage, Bukimi

Tokime - Kaima

Ryu - Gouketsu, Nyororon, Hagure

Keita - Enma

Fuuto PI Future AU

Shotaro gets a call from an old friend, Usumizawa Haruhiko, who calls him to the prestigious Y Gakuen for a new case.  There, the team is tasked with investigating Kirameki Sasuga, who is found to be a Kamen Rider as well. However, the rise of a new type of Dopant called Oniant leads them to team up, with the YSP Watch becoming the Kamen Watch. After defeating the main villain with the help of new faces, they finally relax and the Narumi Detective Agency leaves.

Youkai Rider Enma AU

Takashiro Itsuki is a reclusive but kind teen who gets dragged into chaos when his sister is killed by Tamamo no Mae, and he gets killed while trying to help her. However, Kukuri-hime brings him back with a condition; to use the Youkai Driver she gave him to stop Tamamo-no-Mae and her boss, Soranaki. He is on his own as Youkai Rider Soul until he meets Shin and Tae, from which he meets Shien in the Youmakai. It is there that the fight against Soranaki culminates, and the two unite their souls against the corrupted Tamamo no Mae in order to become Youkai Rider Enma. Following that, the two are named the heirs to the Enma name and Itsuki is revived fully to stop Soranaki. It takes 30 years for that, but soon Itsuki finally defeats him, and he and Shien share a heartfelt goodbye before the Driver is returned to the Youmakai, with Itsuki living on...

Years later, a young child named Amano Keita picks it up, with it having become... the Enma Driver.

Youkai Acknowledgers as Riders AU

An AU where various other characters are aware of Youkai and can turn into Riders.

1. Amano Keita - Whisper, Jibanyan -> Youkai Rider Triple

2. Misora Inaho - USApyon -> Youkai Rider Vader

3. Arima Yuto - Fuu2 -> Youkai Rider Two

4. Akira Emi - Jibanyan -> Youkai Rider Fury

5. Yagami Taichi - Sebastian -> Youkai Rider Perfect

6. Motomiya Daisuke - Fukunyan -> Youkai Rider Gentle

7. Matsuda Takato - Fuankan -> Youkai Rider Justice

8. Kanbara Takuya - Gattenmaiar -> Youkai Rider Support

9. Daimon Masaru - Seiryuu -> Youkai Rider Rain

10. Shinomachi Shin - Suu-san -> Youkai Rider Warrior

11. Takashiro Itsuki - Shien -> Youkai Rider Enma 

12. Arihoshi Tae - Izanagi -> Youkai Rider Life 

14. Amano Keizou - Fuyunyan -> Youkai Rider Hero

15. Miguel Rivera - Raccardo -> Youkai Rider Phantom

16. Nikki Maxwell - Diarinyan -> Youkai Rider Secret

17. Cha Hana - Daidarabocchi -> Youkai Rider Maze Runner

18. Cha Duri - Meramelion -> Youkai Rider Flare

19. Cha Doun - Togenyan -> Youkai Rider Parasite

20. Matsuda Akame/Boboiboy - Youkai Rider Elemental

21. Frisk - Naandenaan -> Youkai Rider Doubt

22. Remy - Nagabana -> Youkai Rider Joker

23. Nishizono Shinsuke - Tengu -> Youkai Rider Sky

24. Makoto Naegi - Sneakinslice -> Youkai Rider Swift Hope

25. Luo Fei - Satori-chan -> Youkai Rider Fortune

26. Fubuki Shirou - Morezou -> Youkai Rider Freeze

27. Hikage Mao -> Youkai Rider Shadow

28.  Hershel Layton - Sherlocnyan -> Youkai Rider Detective

29. Luke Triton - Conyan -> Youkai Rider Puzzler

30. Azusa - Pakkun -> Youkai Rider Demeter

31. Wallace -> Youkai Rider Darkness

32. Jerry - Tomnyan -> Youkai Rider Country

33. Amano Natsume - Shuka -> Youkai Rider Oni

34. Tsukinami Touma -> Youkai Rider Sword

35. Arihoshi Akinori - Suzaku -> Youkai Rider Vermillion

36. Amano Keisuke - Bourei Banchou -> Youkai Rider Gangleader

37. Himeno Ayame - Jorogumo -> Youkai Rider Beauty

38. Ken Ichijouji - Yuray/Lasagnyan -> Youkai Rider Merica