The Betrayal of Zangetsu

The Betrayal of Zangetsu (裏切りの斬月) is the twenty-eighth episode of Kamen Rider Gaim. This episode marks the debut of Mitsuzane Kureshima becoming the second Kamen Rider Zangetsu Shin, as well as Ryoma Sengoku's first on-screen transformation into Kamen Rider Duke.

Synopsis
Takatora reports to Ryoma, Sid, and Yoko that Kouta will be working for them in hunting down the Overlords in an attempt to stop Helheim Forest. They agree to the plan, but the next time they all enter Helheim Forest, Ryoma has set up a trap to take Takatora out of the equation.

Plot
After losing Demushu's trail, Kouta returns to his friends and tells them that Takatora has sided with them with Mitsuzane hiding his displeasure. The next day, though his sister is fine that he does not have a job as he found something that makes him happy, Kouta loses his resumes while he is forced to deal with the Inves.

Luckily, Kouta finds a part-time job at Drupers. In Helheim Forest, as Demushu is being punished for attacking the outsiders, Mitsuzane attempts to kill Kaito to conceal his actions against Kouta. But Kaito explains that while they are enemies, he has no intent to tell Kouta the truth. At the Yggdrasill Corporation, Takatora holds a meeting to discuss hunting down the Overlords for an alternative to Project Ark. After telling Mitsuzane how Kouta restored his hope for the future, they, Yoko, and Sid depart for Helheim Forest in search for the Overlords. However, Zangetsu Shin is attacked by Sigurd and Marika as Ryoma arrives to keep him from escaping.

Realizing he has been betrayed by the conspirators, Takatora tells Mistuzane to report the treachery and help Kouta before he is knocked over a cliff. As Ryoma's group is confident that his older brother is done for, Mitsuzane takes Takatora's Genesis Driver and Melon Energy Lock Seed for his own use. After learning there is no one named Takatora working in Yggdrasill, Kouta returns to Druper to serve Kaito until he is tasked to make a delivery at a site where he is ambushed by Mitsuzane as Zangetsu Shin.

With Kaito coming to his aid, Kouta becomes Gaim Kachidoki Arms to stop the fight between Baron Lemon Energy Arms and Zangetsu Shin to find out what is wrong with the latter. Zangetsu Shin refuses to answer and summons a pack of Inves before escaping. Once the Inves are destroyed, Kaito tells Kouta to stop trusting others so easily while leaving him with a warning to be careful of those he thinks are his friends. Back at the Yggdrasill Corporation headquarters, though believing that he would be unopposed in his goal, Ryoma finds that his laboratory has been destroyed by Sid.

Telling Ryoma and Yoko that he only allied himself with them as they had a mutual enemy in Takatora, Sid explains he is going to obtain the Forbidden Fruit as he escapes through the now closing Crack in the sacred tree.

Cast

 * Kouta Kazuraba (葛葉 紘汰): Gaku Sano (佐野 岳)
 * Mai Takatsukasa (高司 舞): Yuumi Shida (志田 友美)
 * Kaito Kumon (駆紋 戒斗): Yutaka Kobayashi (小林 豊)
 * Mitsuzane Kureshima (呉島 光実): Mahiro Takasugi (高杉 真宙)
 * Takatora Kureshima (呉島 貴虎): Yuki Kubota (久保田 悠来)
 * Zack (ザック): Gaku Matsuda (松田 岳)
 * Peco (ペコ): Saku Momose (百瀬 朔)
 * Ryoma Sengoku (戦極凌馬): Tsunenori Aoki (青木玄徳)
 * Lock Dealer Sid (錠前ディーラー　シド): Kazuki Namioka (波岡 一喜)
 * Yoko Minato (湊 耀子): Minami Tsukui (佃井 皆美)
 * Demushu (デェムシュ): Tomokazu Sugita (杉田 智和)
 * Rosyuo (ロシュオ): Jōji Nakata (中田 譲治)
 * Akira Kazuraba (葛葉 晶): Rika Izumi (泉 里香)
 * Kiyojiro Bando (阪東 清治郎): Tomohisa Yuge (弓削 智久)
 * Sengoku Driver Voice (戦極ドライバー音声), Lockseed Voice (ロックシード音声): Seiji Hiratoko (平床 政治)
 * Genesis Driver Equipment Voice (ゲネシスドライバー各種アイテム音声): Shin-ichiro Miki (三木 眞一郎)
 * Narration (ナレーション): Hōchū Ōtsuka (大塚 芳忠)

Lockseeds

 * Lock Used:
 * Gaim:
 * Orange, Pine, Kachidoki
 * Baron:
 * Lemon Energy
 * Zangetsu Shin:
 * Melon Energy, Himawari
 * Duke:
 * Lemon Energy
 * Sigurd:
 * Cherry Energy
 * Marika:
 * Peach Energy
 * Arms Change:
 * Gaim:
 * Orange Arms, Pine Arms, Kachidoki Arms
 * Baron:
 * Lemon Energy Arms
 * Zangetsu Shin:
 * Melon Energy Arms
 * Duke:
 * Lemon Energy Arms
 * Sigurd:
 * Cherry Energy Arms
 * Marika:
 * Peach Energy Arms