|This article is about a/an episode in Kamen Rider W.|
Who the K Needs/The Devil's Tail (Ｋが求めたもの／悪魔のしっぽ Kei ga Motometa Mono/Akuma no Shippo) is the forty-fifth episode of Kamen Rider W. It is the first part of the 'K' arc, K standing for King, Kazoku (Family) and Kyoko (Todoroki).
A request from a worker at the Futo museum forces Shotaro to find an artifact required by Ryubee for his final master plan.
After seeing the reconstruction on the Futo Tower in the aftermath of its near destruction during a terrorist attack on the city, Shotaro feels it to be a prelude to things to come before being accosted by a woman in Indiana Jones-garb named Kyoko Todoroki, a curator at the Futo Museum who overheard Ryubee trying to find an artifact known as the "Evil Tail" in a excavation site.
She wishes to find it to impress him. Shotaro agrees to take the case, despite Akiko's apprehension in getting involved with the Sonozakis as he sees it to be fate. As Philip and company go to one of the many archaeological dig sites near the Sonozaki mansion to find the Evil Tail, Philip attempts to research the artifact in the Gaia Library, only for the Museum's security measures to prevent him until it suddenly brings up several books on the relating to the Museum, the Gaia Memories, and one about himself.
Fearful to read it, Philip leaves the Gaia Library in terror, just as Wakana arrives and reveals that she removed several restrictions so Philip can have full access to the Gaia Library for the sole purpose of discovering the truth. Back at the dig site, with Akiko using her slippers as dowsing rods, Shotaro finds the box holding the Evil Tail before being suddenly attacked by the Smilodon Dopant, sent by Ryubee to find the item. Becoming Kamen Rider Double, Shotaro fights the Smilodon Dopant as the monster gets the Evil Tail before the Xtreme Memory knocked it off his hands. As CycloneJokerXtreme, Double manages to hit the Smilodon Dopant. However, the Terror Field appears at the dig site, and Ryubee's voice calls out for the Evil Tail.
Though Shotaro wants to settle this, Philip convinces Double to escapes with the two girls. Meanwhile, at the Futo Hotel, Kazu tells Saeko that her father is preparing for the Gaia Impact, a fact that Saeko shows trepidation towards it. Back at the Narumi Agency, Shotaro tries to see what the Evil Tail is to find out Ryubee's plan, but Kyoko will not allow it, refusing to accept Ryubee is a dangerous man.
Though Shotaro apologizes to Philip for saying such things about his father, but Philip realizes he must accept the truth, no matter what it may be as he decides to read the Gaia Library book. By that time, Kyoko runs off to the museum. Ryu and Shotaro follow, while Philip decides to read the book on himself. At the Futo Museum, Kyoko approaches Ryubee as he explains that humanity's ensured future in Earth's history is all he cares about and the Evil Tail will make it a reality. Ryu and Shotaro appear in the museum to confront him, but Ryubee reveals that his true power as the Terror Dopant, having made Shotaro subconsciously unable to fight him due to their previous encounters.
Ryubee then summons the Smilodon Dopant to chase down Kyoko as Ryu pursues as Kamen Rider Accel while Ryubee leaves the frighten Shotaro. Elsewhere, Philip has read the book on him and discovered a horrific revelation. As Accel transforms into Accel Trial to fight the Smilodon Dopant in a losing battle, a terrified Shotaro watches on as Philip arrives and manages to snap him out of his trance as they become Double to fight the Smilodon Dopant. Assuming CycloneMetal on Philip's notion to distract the Smilodon Dopant with Metal Shaft, Double uses the Metal Stag Break Maximum Drive to destroy Mick's Gaia Driver and Smilodon Memory, reverting the Smilodon Dopant back into his feline state.
However, the Terror Dopant arrives, commenting that Philip remembers his purpose with the Evil Tail to initiate the Gaia Impact as Shotaro freezes in fear. Accel Trial intervenes, only for the Terror Dopant to state that he already knows that Ryu is immune to his mind-based attacks, so he conjures the Terror Dragon to attack Accel Trial physically. Kyoko watches on until Wakana finds her with the Evil Tail.
With Shotaro still catatonic, Wakana comments on how Philip has no choice now after reading his book as the Terror Dopant states that he must have learned that real Raito Sonozaki died twelve years ago after falling into the source of the true Gaia Memory, a fact that Philip confirms to Shotaro.
- Shotaro Hidari (左 翔太郎 Hidari Shōtarō): Renn Kiriyama (桐山 漣 Kiriyama Ren)
- Philip (フィリップ Firippu): Masaki Suda (菅田 将暉 Suda Masaki)
- Akiko Narumi (鳴海 亜樹子 Narumi Akiko): Hikaru Yamamoto (山本 ひかる Yamamoto Hikaru)
- Ryu Terui (照井 竜 Terui Ryū): Minehiro Kinomoto (木ノ本 嶺浩 Kinomoto Minehiro)
- Ryubee Sonozaki (園咲 琉兵衛 Sonozaki Ryūbee): Minori Terada (寺田 農 Terada Minori)
- Saeko Sonozaki (園咲 冴子 Sonozaki Saeko): Ami Namai (生井 亜実 Namai Ami)
- Wakana Sonozaki (園咲 若菜 Sonozaki Wakana): Rin Asuka (飛鳥 凛 Asuka Rin)
- Jun Kazu (加頭 順 Kazu Jun): Gong Teyu (コン・テユ Kon Teyu)
- Smilodon Dopant (スミロドン・ドーパント Sumirodon Dōpanto, Voice): Yasuhiro Takato (高戸 靖広 Takato Yasuhiro)
- Narration, Gaia Memory Voice (ナレーション、ガイアメモリ音声 Narēshon, Gaia Memori Onsei): Fumihiko Tachiki (立木 文彦 Tachiki Fumihiko)
- Kyoko Todoroki (轟 響子 Todoroki Kyoko): Yuka Hirata (平田 裕香 Hirata Yuka)
- Raito Sonozaki (Young): Tomoya Hashimoto (橋本 智哉 Hashimoto Tomoya)
- Wakana Sonozaki (Young): Natsuki Kasa (笠 菜月 Kasa Natsuki)
- to be added
- Memory Used:
- Soul - Cyclone, Xtreme
- Body - Joker, Xtreme, Metal
- Half Changes:
- CycloneJoker, CycloneJokerXtreme, CycloneMetal
- Accel, Trial
- Accel, Accel Trial
- to be added
- As part of Super Hero Time, this episode aired alongside Tensou Sentai Goseiger episode 24, Miracle Attack Goseigers.
- Final appearance of Double's CycloneMetal form.