|This article is about a/an episode in Kamen Rider Drive.|
Why Has a New Battle Started? (新たなる闘いはなぜ始まったのか Aratanaru Tatakai wa naze Hajimatta no ka) is the twenty-fifth episode of Kamen Rider Drive. Shinnosuke's identity as Drive is revealed to the public in this episode, and it also marks the debut of Mitsuhide Nira.
Mitsuhide Nira of the 1st Division pays a visit that leaves an unpleasant taste in the Special Unit. Meanwhile, a Roidmude targets Hayase, Shinnosuke's former partner. When things get out of hand, Shinnosuke has no choice but to reveal his identity as Drive to the public.
While the Special Investigation Unit play poker, Mitsuhide Nira, the leader of the 1st Division pays a visit, poorly criticize them and the Unit as a needless division and threatens to shut it down if he didn't get a recent report on them. Shinnosuke spaces out at a park, looking at his old photo with his late father and wished to tell him about all of the cases he solved as a Kamen Rider. He even wanted Drive to fully become a part of the police forces but Mr. Belt (through Shift Speed) denies it, fearing that Roidmudes will infiltrate the police forces and eliminate Drive from within. Shinnosuke received a phone call that a wave of Heavy Acceleration just detected.
At said location, Roidmude 007 had just break free Hajime Taga, a prisoner and offered him an absolute power by combining with him. Accepting 007's offer, he becomes the Sword Roidmude and tried to attack the decelerated police forces before Kamen Riders Drive and Mach stopped him. Sword flees from them, having known whom he will after next. While the police forces approached Drive in astonishment, Kiriko spotted Chase and sent Justice Hunter after him. Heart and Medic discuss the news of 007 fusing with a human to evolve. Knowing Brain won't be too smart to create the new Viral Core, Heart suddenly knows who is the true mastermind.
Now knowing a new type of evolution 007 has gone through, the Drive Pit crews discuss this matters and debating on how to eliminate 007 without killing the human. As Go decided to track Sword on his own, Rinna offered herself to modify the Drive Driver to set it to killing Roidmudes, though still needed a sample of an Advanced Roidmude. Shinnosuke suddenly realised that he's late for meeting with Kiriko decided to go off while getting the sample of an Advanced Roidmude. During the meeting at the Unit's office, 1st Division officers expressed their apology to Genpachiro for not believing the existence of Kamen Rider and Roidmudes, revealing that they were the ones whom laughed him in one episode. Nira stopped them and tried to claim back his men while urging the unit to apprehend Hajime.
While patrolling with Gen via Tridoron, Shinnosuke quietly excited that the whole division had at least tried to gave the Kamen Riders their support, despite being unable to transform into Drive when nearby. Shinnosuke suddenly stopped the car remembering Hajime clearly. Sometime before the Global Freeze, Hajime had just killed a police officer. He was quickly arrested by Shinnosuke's former partner, Akira Hayase. This makes Hayase as his current target. As Shinnosuke phoned and warned Hayase at his hospital, the latter agreed but urged Shinnosuke to come faster as he doesn't want more patients to become victims. Kiriko approached to Chase and asked him for his help. Chase confused, since he is a Roidmude, followed by multiple of his assassination attempt on her and Drive but she still trust him, even Kyu Saijo revealed himself, having sent by Shinnosuke to spy on Kiriko and told that he even believed that Roidmudes were not so evil since he encountered one. Chase transformed into Mashin Chaser and rips off one of his Violet Guard to Kiriko as a sign of cooperation before leaving. Kiriko phoned Rinna later on much to Saijo's shock.
Sword started to attack the hospital and nearly killed Hayase until Tridoron appeared and for Shinnosuke and Gen saved him. Kamen Rider Mach appeared and fights him but still unable to fully kill Sword due to being partially human. As Rinna arrived with the Drive Driver, Shinnosuke forced to transform into Drive in front of multiple onlookers, including Gen and Kyu. Drive fights Sword in Type Speed, followed by Type Formula Sparner before reverting back and separated 007 from Hajime with Speedrop. As 007 tried to get away, Drive jump into the ejected Tridoron cabin and eliminated him with Drift Slash. Luckily, his Core was saved by Roidmude 001. Shinnosuke quickly arrested Hajime for escaping custody and attempted murder.
Mach approached Gen and Kyu, revealing him as Go much to their shock. News of Hajime's apprehension reached Nira, even surprising him with the fact that Shinnosuke is Kamen Rider Drive. Shinnosuke showed Gen and Kyu the Drive Pit. Jun appeared, having known Krim as his former colleague and that the Special Investigation Unit's formation was his plan all along to help Drive. Shinnosuke relieved over the fact that he will never stressed over his double life as Drive but Jun even made Drive's secret identity to the public much to their shock.
- 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)
- Akira Hayase (早瀬 明 Hayase Akira): Yukihiro Takiguchi (滝口 幸広 Takiguchi Yukihiro)
- Mitsuhide Nira (仁良 光秀 Nira Mitsuhide): Kisuke Iida (飯田 基祐 Iida Kisuke)
- 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)
- Medic (メディック Medikku): Fumika Baba (馬場ふみか Baba Fumika)
- Roidmude 007 (ロイミュード００７ Roimyūdo Zero Zero Nana, Voice): Takashi Ōhara (大原 崇 Ōhara Takashi)
- Hajime Taga (多賀 始 Taga Hajime)/Sword Roidmude: Mitsuyoshi Tani (谷 充義 Tani Mitsuyoshi)
- Police Officers: Tomoyuki Inoue (井上 智之 Inoue Tomoyuki), Mitsunori Katsu (勝 光徳 Katsu Mitsunori)
- Eisuke Tomari (泊 英介 Tomari Eisuke): Tareyanagi (たれやなぎ)
- Shinnosuke Tomari (Teen): Ryohei Aoki (青木 綾平 Aoki Ryōhei)
- Police: Masashi Takada (高田 将司 Takada Masashi)
Shift Cars & Signal Bikes
- Car Used:
- Type Change: Shift Speed, Shift Formula
- Tire Exchange: Dream Vegas, Sparner F03
- Type Used:
- Type Speed, Type Speed Vegas, Type Formula, Type Formula Sparner
- Bike Used:
- Form Change: Signal Mach
- Signal Exchange: Signal Kaksarn
- Form Used:
- Mach, Mach Kaksarn
- When Shinnosuke becomes both Type Speed and Type Formula, the sort of song that would come after Mr. Belt announcing the form name, comes just as Mr. Belt announces "Drive".
- As part of Super Hero Time, this episode aired alongside Shuriken Sentai Ninninger episode 7, Shinobi 7: Spring Ninja Festival!.
- Viewership: 7.0%
- Closing Screen Shift Car/Signal Bike
- Roidmude Count
- Answer to the episode's question: Because of the emergence of the Neo Viral Cores and the subsequent reveal of Drive's identity.
- This episode marks the re-debut of Roidmude 001 since the first episode of Kamen Rider Drive (not counting the flashback from the tenth episode).
- Roidmude 007's use of a Neo Viral Core to fuse with Hajime Taga and evolve into the Sword Roidmude as seen here was previewed earlier in the online recap special Kamen Rider Drive Vs. the Terrifying Zunbo Ganbo Roidmude.
- This is the first episode where neither Drive nor Mach use the Shift Deadheat Car since its debut in episode 16.
- This episode reveals that the used Shift Tire does in fact return to Tridoron's left front wheel.
- When Shinnosuke is talking with Hayase, he says that he's a "detective and a Kamen Rider", which was said in various trailers before the start of Kamen Rider Drive.
- This episode marks the return of Drive Type Speed's Tridoron-backed Speedrop, which made its first and last appearance way back in episode 1. Sadly, like it's first debut, the attack isn't capable of damaging a Roidmude's Core.
- Rinna's modification of the Drive Driver which allows Drive's Full Throttle finisher to seperate the human host from the Roidmude to prevent harming them before he destroys the monster is a similar concept used for the Maximum Drive and Limit Break performed by the Riders in W and Fourze.
- The fusion of the Roidmude with a human host is also similar to that of the feline-based Yummies created by the Greeed Kazari in Kamen Rider OOO. The method of seperation used by OOO and Birth was to weaken the Yummy enough to create an opening allowing them to physically pull out the host from the Yummy's body.
- This is the first time Drive changes from Type Speed to Type Formula.
- It is also the only time Drive changes from Type Formula Sparner to Type Speed.
- This is the last time Chase changes from his Protozero form to his Mashin Chaser form.
- Final appearance of Drive Type Speed Vegas and Type Formula Sparner, as well as Mach Kaksarn.
Kamen Rider Drive Volume 7 features episode 25-28: Why Has a New Battle Started?, Where is Chaser Going?, What's Go Shijima's Reason to Fight? and Why Were the Families Targeted? 
Collection 3 comes with 12 episodes.