Henshin

"Henshin!" (変身) is the Japanese word for "transformation/transform" meaning "to change or transform the body" or "equip". In Kamen Rider and Power Rider (in the latter, the phrase is used frequently by fanon writer Hyperus18), it is a common transformation call for what a Rider shouts when they are about to transform. It is said to have been the suggestion of producer Toru Hirayama, based on the Japanese title of Franz Kafka's Metamorphosis, which features a man transformed into an inhuman, bug-like creature against his will, a recurring theme of the Kamen Rider series.

The first use of the phrase was by Hayato Ichimonji, as his predecessor Takeshi Hongo did not have a transformation call before that. It has since become an integral aspect rooted within the Kamen Rider series.

Generally, most Kamen Riders call out "Henshin!" during their transformation sequences. Variations of this phrase have been used by various Riders, either when transforming or switching between forms. These include:
 * Kamen Rider 1 and Kamen Rider Dark Ghost: "Rider Henshin!" (ライダー変身!)
 * Kamen Rider V3: "Henshin...V3!" (変身...V3!)
 * Kamen Rider X: "Dai Henshin" (大変身)
 * Kamen Rider Stronger: "Henshin...Stronger!" (変身...ストロンガー!)
 * Skyrider: "Sky Henshin" (スカイ変身)
 * Kamen Rider Kuuga: "Cho Henshin" (超変身) (when changing forms)
 * Kamen Rider Mach or Hyperus18 Power Riders whenever they transform together: "Let's... Henshin!" (レッツ... 変身!)
 * Kamen Rider Ex-Aid: "Dai Henshin" (大変身) (Level 2, varies with each higher level up to lv. 20), "Max Dai Henshin" (マックス大変身) (Level 99), "Hyper Dai Henshin" (ハイパー大変身) (Muteki Gamer)
 * Kamen Rider Para-DX: "Dai Henshin" (大変身) (when switching between his lv.50 forms), "Max Dai Henshin" (マックス大変身) (lv. 99)

Some Riders use normal "Henshin!" but also have variation in some occasion. Examples are Kamen Rider Joker saying "I... Henshin" (俺... 変身) in episode 49 of Kamen Rider W and Kamen Rider Grease saying "Dekiteruyo." (できてるよ.) when using the Build Driver with the Grease Blizzard Knuckle.

Other than "Henshin" and variations of the phrase, other characters, including Riders and Rider-like characters, have used different catchphrases in a similar fashion when transforming or switching between forms. These include:
 * Kamen Rider X: "Set up!" (セットアップ)
 * Masked Rider: "Ectophase Activate!"
 * Kamen Rider G3-X: "G3-X Equip!" (G3-X 装着!)
 * Kabuki, Touki, Nishiki, Habataki, Kirameki: By calling out their respective Oni names during their transformation.
 * Ventaran Kamen Riders: "Kamen Rider!"
 * Kamen Rider Amazon (the original), Amazon Omega, Amazon Alpha, Amazon Sigma, Amazon Neo & Crow Amazon: "Amazon."
 * Graphite & Lovelica Bugster: "Baiyou" (培養)
 * Ride Player Nico: "Game Start!" (ゲームスタート)
 * Kamen Rider Build: "Build Up!" (ビルドアップ) (when changing forms)
 * Night Rogue & Blood Stalk: "Jouketsu" (蒸血)
 * Bikaiser: "Kaiser!" (カイザー) and later "Bikaiser" (バイカイザー)
 * Engine Bros. & Remocon Bros./Hell Bros.: "Jundou" (潤動)
 * Kamen Rider Zi-O: "Armor Time!" (アーマータイム) (only in Kamen Rider Build: Be The One to transform into Build Armor)
 * Dodo Magia: "Assassinate." (暗殺)

There are some Kamen Riders who do not speak or call out any phrase during their transformation. These include:
 * Kamen Rider 1 (during his initial transformation in the first 13 episodes of the original series)
 * Riderman
 * Kamen Rider Shin
 * Kamen Riders from Kamen Rider The First and Kamen Rider The Next
 * Kamen Rider G3 (before becoming G3-X via upgrades)
 * All of the Oni Riders in Kamen Rider Hibiki

Also there are some Riders that usually call out but not during some of their transformation. Examples include Yusuke Godai/Kamen Rider Kuuga, Shinji Kido/Kamen Rider Ryuki and Kouta Kazuraba/Kamen Rider Gaim in their first transformations.