|This article is about a/an episode in Kamen Rider Drive.|
Why Won't My Little Brother Put On the Brakes? (私の弟にはなぜブレーキがないのか Watashi no Otōto ni wa Naze Burēki ga Nai no ka) is the thirteenth episode of Kamen Rider Drive. This episode features the debut of Mach's Kikern, Tomarle, and Kaksarn forms.
Kiriko wonders about her brother's arrival and true intentions when a group of thieves is discovered using a device that creates Heaviness.
At the Drive Pit, Mr. Belt contacted his mentor, Professor Harley Hendrickson where he asked on why did Go returned to Japan. Harley furiously revealed that Go went out in the middle of his training and requested the team to look after him. According to Rinna, Mach is Harley's new system which was said to surpass Krim's Drive system. Kiriko furiously kicked the whole pit and yelled at Mr. Belt for hiding the fact that he planned to use her brother as his new candidate without her knowledge. Go even teases her sister and Shinnosuke (much to Rinna's jealousy) and ended up with both of them argued. The two siblings visited their mother's memorial, Go resolved not to live with Kiriko due to his own behaviour and for her sister's safety, since they only had each other after their parents' death.
At the Special Investigation Unit, a group of robbers broadcast their next robbery Kuruma Credit Union and challenged the police forces to stop them since they had the same Slowdown bracelet which previously worn by Naoki Todagawa. Combined with Kyu's mentions that no Slowdown detections on radar lately, this means that Naoki's case was an example. About half an our before the robbery, Genpachiro and Shinnosuke interrogate Naoki on the information for whom had selling the Slowdown wristbands. Naoki revealed that he had no idea on who sold him the item, meaning those wristbands will automatically trigger a memory eraser to assure it's secret.
In the Roidmude's hideout, Medic revealed that Gunman and Roidmude 018 impersonated as a pair of major underworld traffickers. 018 sells the device and Gunman acted as his bodyguard. Heart sent Chase to guard 018 until he evolves. Chase agreed but he grew skeptical with his number and the point of him had no memories of Global Freeze. Genpachiro hired SWAT officers at Kuruma and the robbers on their way. But Go/Mach stopped them, released his own Heavy Acceleration and rob them of their Slowdown wristbands. Shinnosuke/Drive arrived and stopped him. Go surrenders as he switch off the Heavy Acceleration. He angrily scolded Go for using it despite his good intentions but Go calmly question him that they were even with the Roidmudes since both are powered by the same source.
Captain Jun returned from his vacation and Go appeared in the Special Investigation Unit by revealing his snapshot of Mach. Shinnosuke and the Drive Pit crews brought him away as Go explained that he got his Signal Bikes to capture his picture. Mr. Belt explained that, Mach Driver Honoh was made based on the aspects of Drive Driver but it also had its own AI much like Krim's role in Drive Driver. Shinnosuke suddenly realised something and sent the Shift Cars in a search for Go. Go at the same time quickly infiltrated the Roidmudes' base and destroy their Slowdown wristbands. As Gunman, 018 and Chase about to kill him, he was saved by Kiriko and Shinnosuke. The latter revealed that Go/Mach used Heavy Acceleration to remove the trio robbers' bracelet to interrogate their secrets before they lost their memory, since he had familiar with their operations back at America.
Shinnosuke as Drive transformed and battle Mashin Chaser while the Roidmude brothers attempted to attack the Shijima siblings. Mr. Belt realised that Mashin Chaser's number is 000/Protozero, hinting an upcoming secret. Signal Bikes came to aid Go and remove 018's Slowdown wristbands, figuring out that 018 had produced them. Go transformed into Mach and outsmart the two brothers. He assumed Mach Kikern and summon a demon beast to attack them. He switched to Mach Tomarle and finally Mach Kaksarn. He used Full Throttle to destroy their bodies followed by their Core as Mach Magarl. Before Mashin Chaser could attack Mach, Medic appeared and spirited him away. At the cafeteria, Shinnosuke started to accept Go's friendship along with the term big brother.
- 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)
- Chase (チェイス Cheisu): Taiko Katono (上遠野 太洸 Katōno Taikō)
- Go Shijima (詩島 剛 Shijima Gō): Yuu Inaba (稲葉 友 Inaba Yū)
- 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)
- Narration (ナレーション Narēshon), Drive Driver's voice (ドライブドライバーの声 Doraibu Doraibā no koe): Chris Peppler (クリス・ペプラー Kurisu Pepurā)
- Heart (ハート Hāto): Tomoya Warabino (蕨野 友也 Warabino Tomoya)
- Brain (ブレン Buren): Shota Matsushima (松島 庄汰 Matsushima Shōta)
- Medic (メディック Medikku): Fumika Baba (馬場ふみか Baba Fumika)
- Naoki Todagawa (戸田川 直樹 Todagawa Naoki): Pachiku Kato (加藤 パーチク Katō Pachiku)
- Gunman Roidmude (ガンマンロイミュード Ganman Roimyūdo): Bernard Ackah (ベルナール・アッカ Berunāru Akka)
- Dark Merchant (元締め Mototsume)/Roidmude 018: Marvin Jr. (マービンJr. Mabin Jyunia)
- Harley Hendrickson (ハーレー·ヘンドリクソン Hārē Hendorikuson, Voice): Ulf Ōtsuki (大月 ウルフ Ōtsuki Urufu)
- 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)
- Heaviness Robbers (どんより強盗団 Donyori Gododan): Hajime Kanzaki (神前 元 Kanzaki Hajime), Daisuke Satō (佐藤 太輔 Satō Daisuke), Satoshi Fujita (藤田 慧 Fujita Satoshi)
Shift Cars, Signal Bikes, & Viral Cores
- Car Used:
- Type Change: Shift Speed, Shift Wild
- Tire Exchange: N/A
- Type Used:
- Bike Used:
- Form Change: Signal Mach
- Signal Exchange: Signal Kikern, Signal Tomarle, Signal Kaksarn, Signal Magarl
- Form Used:
- Mach, Mach Kikern, Mach Tomarle, Mach Kaksarn, Mach Magarl
- Core Used:
- Chaser Spider
- Tune Form Used:
- Tune Chaser Spider
- As part of Super Hero Time, this episode aired alongside Ressha Sentai ToQger episode 43, Station 43: The Locked Door.
- Viewership: 5.3%
- Closing Screen Shift Car/Signal Bike
- Roidmude Count
- Answer to the episode's question: Shinnosuke is Go's brakes.
- The opening credits are updated to include Kamen Rider Mach.
- A running gag occur in this episode where Rinna Sawagami gets jealous whenever Shinnosuke and Kiriko are alone.
- As revealed in the 20th episode, the Kyu that appears in this episode is actually Roidmude 072.
- This is the first episode where Drive doesn't assume any version of Type Technic.
- This is the last episode to debut new Signal Exchange modes for Mach.
- It is also the only time Mach changes into all of his Signal Exchange forms.
- to be added
Kamen Rider Drive Volume 4 features episode 13-16: Why Won't My Little Brother Put On the Brakes?, Who Is the Black Shadow Chasing Her?, When Will These Feelings Reach You? and Why is Rinna Sawagami Nervous? 
Collection 2 comes with 12 episodes.
- TV Asahi's official summary for 「私の弟にはなぜブレーキがないのか」
- Toei TV's official episode guide for 「私の弟にはなぜブレーキがないのか」