|This article is about a/an episode in Kamen Rider Gaim.|
The Invasion Begins with the End of the World (世界のおわり はじまる侵略 Sekai no Owari Hajimaru Shinryaku) is the twentieth episode of Kamen Rider Gaim.
Takatora shows Kouta the truth behind Helheim Forest, at the same time Kaito would learn the same thing from Ryoma, Sid, and Yoko. Meanwhile in Zawame City, more Inves invade and it's up to Mitsuzane and Zack to stop them.
Takatora guides Kouta to an ancient city deep inside Helheim Forest, revealing that the place must be the home of an alien civilization that was destroyed when the forest's plants had spread through it, transforming all life into Inves after they ate the fruit. Meanwhile, Ryoma reveals this information to Kaito, as well, and adds that the Yggdrasill Corporation is just a front to cover their real purpose, which is to prevent the Helheim Forest from taking over the world. Kaito also discovers that the Yggdrasill Corporation is using the sacred tree from Mai's family's shrine to open a Crack into the Helheim Forest, much to his anger, and Ryoma reveals that the tree is not of this world, thus making it necessary for their goals. Elsewhere, Armored Rider Knuckle defeats some Inves, but fails to protect some passerby from being infected, when Oren and Jonouchi appears to try to turn the public against him, just to be interrupted when more Inves appear. Back at Helheim Forest, Takatora claims that should Yggdrasill fail to stop the plants' invasion, they could at least buy around ten more years for mankind and only those capable to fight it must know the truth until the last moment in order to prevent further chaos in the world, but Kouta disagrees. When more Inves appear to fight them, Zangetsu Shin defeats the monsters by himself, as Gaim is unsure about fighting them, knowing that they were once ordinary living beings. When Ryoma finishes his explanation, Kaito claims that instead of just protecting the weak, they should take advantage of the situation to ensure that only the strong survive, and Ryoma, Sid and Yoko all reveal that they have the same intent, despite the Yggdrasill Corporation's goals in mind, welcoming him among their ranks.
- Kouta Kazuraba (葛葉 紘汰 Kazuraba Kōta): Gaku Sano (佐野 岳 Sano Gaku)
- Mitsuzane Kureshima (呉島 光実 Kureshima Mitsuzane): Mahiro Takasugi (高杉 真宙 Takasugi Mahiro)
- Kaito Kumon (駆紋 戒斗 Kumon Kaito): Yutaka Kobayashi (小林 豊 Kobayashi Yutaka)
- Mai Takatsukasa (高司 舞 Takatsukasa Mai): Yuumi Shida (志田 友美 Shida Yuumi)
- Zack (ザック Zakku): Gaku Matsuda (松田 岳 Matsuda Gaku)
- Peko (ペコ Peko): Saku Momose (百瀬 朔 Momose Saku)
- Chucky (チャッキー Chakkī): KANON
- Hideyasu Jonouchi (城乃內 秀保 Jonouchi Hideyasu): Ryō Matsuda (松田 凌 Matsuda Ryō)
- Oren Pierre Alfonzo (凰蓮・ピエール・アルフォンゾ Ōren Piēru Arufonzo): Metal Yoshida (吉田 メタル Yoshida Metaru)
- Yoko Minato (湊 耀子 Minato Yōko): Minami Tsukui (佃井 皆美 Tsukui Minami)
- Takatora Kureshima (呉島 貴虎 Kureshima Takatora): Yuki Kubota (久保田 悠来 Kubota Yūki)
- Lock Dealer Sid (錠前ディーラー シド Jōmae Dīrā Shido): Kazuki Namioka (波岡 一喜 Namioka Kazuki)
- Ryoma Sengoku (戦極 凌馬 Sengoku Ryōma): Tsunenori Aoki (青木 玄徳 Aoki Tsunenori)
- Sengoku Driver Equipment Voice (戦極ドライバー各種アイテム音声 Sengoku Doraibā Kanren Aitemu Onsei): Seiji Hiratoko (平床 政治 Hiratoko Seiji)
- Genesis Driver Equipment Voice (ゲネシスドライバー各種アイテム音声 Geneshisu Doraibā Kanren Aitemu Onsei): Shin-ichiro Miki (三木 眞一郎 Miki Shinichirō)
- Narration (ナレーション Narēshon): Hōchū Ōtsuka (大塚 芳忠 Ōtsuka Hōchū)
- Yggdrasill Employee: Toshihiro Ogura (おぐら としひろ Ogura Toshihiro), Hideki Komabashiri (駒走 秀樹 Komabashiri Hideki)
- Dancer: Ryoko Shimizu (清水 涼子 Shimizu Ryōko), Kei Namiki (並木 桂 Namiki Kei), Saki Kitakubo (北久保 咲紀 Kitakubo Saki), Chisato Maruyama (丸山 千怜 Maruyama Chisato)
- Lock Used:
- Zangetsu Shin:
- Melon Energy
- Arms Change:
- As part of Super Hero Time, this episode aired alongside Ressha Sentai ToQger episode 3, Station 3: Desperate Once Convinced.
- Viewership: 4.6%
- Closing Screen Lockseed Collection:
- This episode begins the Helheim Saga, the third story arc of the series.
- This is the first episode where Gaim does not transform into Jimber Lemon Arms since its debut in episode 16.
- This episode reveals what Mitsuzane saw during his visit to the Helheim Forest with his brother back in The New Arms! Jimber Lemon is Born!.
- This episode marks the first time an Armored Rider and a New Generation Rider transform together.
- The outside view of the ancient civilization in ruins within Helheim Forest slightly resembles Machu Picchu.
- TV Asahi's official summary for 「世界のおわり はじまる侵略」
- Toei TV's official episode guide for 「世界のおわり はじまる侵略」