|This article is about a/an episode in Kamen Rider Drive.|
What is a Kamen Rider? (仮面ライダーとはなにか Kamen Raidā to wa Nani ka) is the second episode of Kamen Rider Drive. It introduces Shift Justice Hunter, debuting Drive Type Speed Hunter, as well as featuring the first appearance of Brain and Chase. Spin Mixer and Massive Monster make a brief appearance in this episode.
After transforming into Kamen Rider Drive and discovering the strange occurences throughout the city are caused by the Roidmude, Shinnosuke seeks out more information from his former colleague Hayase while the Roidmude named Heart revives Roidmude 029 after he has been defeated by Drive.
Mr. Belt dreamed himself on the night of his death. As three Roidmudes approach him, one of them transformed into a human and begin to killed Belt's human identity, Krim Steinbelt. Kiriko catched a slacking Shinnosuke with the help of Justice Hunter. Shinnosuke begins to doubt himself that using Mr. Belt's power, he could fight the Roidmudes, meaning all of them including the Shift Cars are from the same source. Heart met the Roidmude Commander Brain in a cafe and reported him of his deed: granting Roidmude 029 a new body.
In an office, a Cobra Viral Core search through several people in the computer and reverted back to Roidmude 029 once he got what he needed. Mr. Belt spied on Shinnosuke via Shift Speed Shift Car, whom visited his old friend Akira Hayase and still bore the guilt for the accidents 6 months prior. But Akira never minded it, instead told him to use that guilt as a motivation in his job. After Akira accidentally dropped his packet of painkiller pills, Shinnosuke finally identify the Roidmude's main goal. Returning to the Special Investigation Unit, Shinnosuke revealed that the victims are all mistake from the murder cases. The Roidmude's target was Nobou Masuda, and his main goal is to get healthy human bodies and the victims that turned red was all failures, evident by their medicine packets. Shinnosuke realised the first victim of the Roidmude had his girlfriend missing.
With the help of the Special Investigation Unit members, they managed to search the Roidmude's base in a closed amusement park. Roidmude 029 appeared again, revealing that his desire is to collect ideal human parts to create his ideal human body. He evolved into the Iron Roidmude and sent a wave of Heavy Acceleration. Realised of his evolution, Heart and Brain quickly went to the scene. As Iron Roidmude went away, Shinnosuke chased them but stopped by Roidmude 093 and Roidmude 071 until Mr. Belt arrived and Shinnosuke transformed into Drive. He drove the Tridoron and chased them where they blocked him with several obstacles which he managed to get pass trough. With the help from Shift Cars Max Flare, Funky Spike and Midnight Shadow, they destroy 093 and 071. Drive pursued Iron easily with Type Speed Shadow and Type Speed Hunter, blocking his attacks with the Justice Cage and killing him with the JustiSmash Full Throttle. Iron asked him either he is a Kamen Rider before exploded and his Core vanished. Heart and Brain realised that 029/Iron was terminated and called Chase to find out the problem.
In the Special Investigation Unit, Shinnosuke asked Kiriko what is the title Kamen Rider meant. She smiled, but try to deny the fact due to her known cold personality. Mr. Belt overheard the arguement and decided to call it as Kamen Rider Drive.
At night, a woman distraught to find several ghosts flying in the sky and a mysterious Roidmude attack the woman.
- Shinnosuke Tomari (泊 進ノ介 Tomari Shinnosuke): Ryoma Takeuchi (竹内 涼真 Takeuchi Ryōma)
- Kiriko Shijima (詩島 霧子 Shijima Kiriko): Rio Uchida (内田 理央 Uchida Rio)
- Jun Honganji (本願寺 純 Honganji Jun): Tsurutaro Kataoka (片岡 鶴太郎 Kataoka Tsurutarō)
- Rinna Sawagami (沢神 りんな Sawagami Rinna): Rei Yoshii (吉井 怜 Yoshii Rei)
- Kyu Saijo (西城 究 Saijō Kyū): Kenta Hamano (浜野 謙太 Hamano Kenta)
- Genpachiro Otta (追田 現八郎 Otta Genpachirō): Taira Imata (井俣 太良 Imata Taira)
- Akira Hayase (早瀬 明 Hayase Akira): Yukihiro Takiguchi (滝口 幸広 Takiguchi Yukihiro)
- Chase (チェイス Cheisu): Taiko Katono (上遠野 太洸 Katoono Taikō)
- Brain (ブレン Buren): Shota Matsushima (松島 庄汰 Matsushima Shōta)
- Heart (ハート Hāto): Tomoya Warabino (蕨野 友也 Warabino Tomoya)
- Krim Steinbelt / Drive Driver's voice (クリム・スタインベルト / ドライブドライバーの声 Kurimu Sutainberuto / Doraibu Doraibā no koe), Narration (ナレーション Narēshon): Chris Peppler (クリス・ペプラー Kurisu Pepurā)
- Nobuo Masuda (益田 信夫 Masuda Nobuo)/Roidmude 029 (Iron Roidmude) (ロイミュード０２９ (アイアンロイミュード) Roimyūdo Zero Ni Kyū (Aian Roimyūdo)): Masafumi Yokoyama (横山 真史 Yokoyama Masafumi)
- Iyo Sawai (澤井 伊代 Sawai Iyo)/Roidmude 029 (Iron Roidmude) (ロイミュード０２９ (アイアンロイミュード) Roimyūdo Zero Ni Kyū (Aian Roimyūdo)): Maari (麻亜里)
- Nina Kusaragi (如月 仁奈 Kusaragi Nina): Hitomi Isaka (井坂 仁美 Isaka Hitomi, Kamen Rider Girls)
- Satsuki Yamabuki (山吹 沙月 Yamabuki Satsuki): Mitsuki Endo (遠藤 三貴 Endō Mitsuki, Kamen Rider Girls)
- Housewife: Keiko Shinohe (しのへ けい子 Shinohe Keiko)
- Victim: Meru Mizusawa (水沢 芽瑠 Mizusawa Meru)
- Man with the car: Takeshi Date (伊達 剛 Date Takeshi)
- Kamen Rider Drive: Seiji Takaiwa (高岩 成二 Takaiwa Seiji)
- Roidmude 029/Iron Roidmude: Yohei Fujita (藤田 洋平 Fujita Yohei)
- Roidmude 071: Daisuke Satō (佐藤 太輔 Satō Daisuke)
- Roidmude 084: Yugo Fujii (藤井 祐伍 Fujii Yūgo)
- Roidmude 084: Tatsuya Kaneko (金子 起也 Kaneko Tatsuya)
- Car Used:
- Type Used:
- Type Speed, Type Speed Shadow, Type Speed Hunter
- As part of Super Hero Time, this episode aired alongside Ressha Sentai ToQger episode 32, Station 32: Determination.
- Viewership: 6.3%
- Closing Screen Shift Car Collection:
- Roidmude Count
- Answer to the episode's question: An enemy of the Roidmudes, like Drive.
- Since Kamen Rider Fourze, this is the first time in the TV series that a Rider is actually referred to as a "Kamen Rider" (not including the special episodes of Wizard).
- In the episode, Heart steals a red 1978 Cadillac convertible to find Brain. The car is a recycled prop from the movie Kamen Rider Blade: Missing Ace. In that film, it belonged to Kotaro Shirai.
- It might be the reference that why Heart will used a red Shift Car named "Heartron" to transform into Kamen Rider Heart in Kamen Rider Drive Saga: Kamen Rider Heart.
- Despite being crushed under the pipe during the Global Freeze incident prior to the beginning of the series, Hayase still survived from the collapse with only a broken leg.
- It is possible the deceleration effect of the Global Freeze slowed the velocity of the debris enough to reduce the force of impact, otherwise Hayase's injuries would have been fatal.
- While Shinnosuke and Kiriko are waiting for the traffic lights to go green, Kamen Rider AccelTrial's countdown sound can be heard.
- Keiko Shinohe previously portrayed Tomoko's mother Haruko in episode 10 of Kamen Rider Fourze.
- This episode marks the only time Drive Type Speed Hunter initiates Justismash to defeat a Roimude, without using any weapons.
- Kamen Rider Drive Volume 1 features episode 1-4: Why Did My Time Stop?, What is a Kamen Rider?, Who Stole the Woman's Smile? and What is That Prideful Chaser Thinking? 
- Blu-Ray Collection 1 comes with 12 episodes.