Why Must They Fight?

Why Must They Fight? (彼らはなぜ戦わなければならなかったのか) is the forty-sixth episode of Kamen Rider Drive. This episode features the debut appearance of Kamen Rider Chaser Mach, a fusion form between Kamen Riders Mach and Chaser, as well as the proper debut of the Sigma Circular in mecha form. This also marks the final appearances of Medic and Tenjuro Banno.

Synopsis
Chase protected Go in exchange for his life. Only after seeing him perish does Go realize the impact Chase had on him. Then, Gold Drive, whom Chase supposedly used his final strength to defeat, appears before him. Meanwhile, Shinnosuke heads for the rooftop of the SSDC alongside Heart and Medic. A device that would turn humanity into data, the Sigma Circular, is there. However, right before they could reach the place, the second Global Freeze hits…

Plot
Rinna and Genpachiro manages to cut the building's power source, allowing Shinnosuke and the executives to get in. Despite Chase's death,  Gold Drive still survives the kamikaze attempt, prompting Mach to fight him again. Having finally acknowledges Chase as his friend, he used the Signal Chaser Bike to become Kamen Rider Chaser Mach and seemingly defeated Gold Drive, destroying the hijacked body of 006. Kiriko reunites with Go and delighted over his victory but her happiness cut short after discovering Chase's death.

After Drive, Heart and Medic defeated the remaining three Reaper Legionnaires, Medic tried to save their Cores but they instead exploded and soon realized that she had lost this ability ever since she woke up, hinting it as Banno's final trap. Shinnosuke receives a call from Kiriko of Gold Drive's death. As the last two Roidmudes mourn of Chase's demise, the second Global Freeze has taken action, but as they tried to advance, Medic was forced to be left behind after she suddenly weakened not even a second after she re-assumed her Super Evolved form. Meanwhile, Banno appears to have survived in his Driver despite Gold Drive's defeat but before his mind can be transferred again, Go kills him with the Shingou-Ax. Once done, Go gives Kiriko Shift Dead Heat and orders her to get to Shinnosuke.

Reaching the Sigma Circular, Drive and Heart arrived too late as Sigma finally evolves and attacks the pair with blistering speed and great power. At the same time, victims of Heavy Acceleration are slowly digitizing from Sigma's power. As the machine utilizes the power of all four Super Evolved Core Driviars, Heart and Drive plan a simultaneous attack but failed. A weakened Medic appears and her body disintegrates but in her final moments, Medic's Core assumes the form of the goddess she was from the first Global Freeze, healing Shinnosuke before evaporated into nothingness. In rage, Shinnosuke transforms into Type Tridoron and stood up to continue the battle to end Banno's madness.

Cast

 * Shinnosuke Tomari (泊 進ノ介): Ryoma Takeuchi (竹内 涼真)
 * Kiriko Shijima (詩島 霧子): Rio Uchida (内田 理央)
 * Go Shijima (詩島 剛): Yuu Inaba (稲葉 友)
 * Jun Honganji (本願寺 純): Tsurutaro Kataoka (片岡 鶴太郎)
 * Rinna Sawagami (沢神 りんな): Rei Yoshii (吉井 怜)
 * Kyu Saijo (西城 究): Kenta Hamano (浜野 謙太)
 * Genpachiro Otta (追田 現八郎): Taira Imata (井俣 太良)
 * Narration (ナレーション), Drive Driver's voice (ドライブドライバーの声): Chris Peppler (クリス・ペプラー)
 * Heart (ハート): Tomoya Warabino (蕨野 友也)
 * Medic (メディック): Fumika Baba (馬場ふみか)
 * Tenjuro Banno (蛮野 天十郎): Masakazu Morita (森田 成一)

Guest cast

 * Sigma Circular (シグマサーキュラー): Ayumi Fujimura (藤村 歩)

Shift Cars, Signal Bikes & Viral Cores

 * Car Used:
 * Type Change: Shift Tridoron
 * Tire Exchange: N/A
 * Type Used:
 * Type Tridoron
 * Tire Blending used in Type Tridoron:
 * Kouji Genbar
 * Bike Used:
 * Form Change: Signal Mach, Signal Chaser
 * Signal Exchange: N/A
 * Form Used:
 * Mach, Chaser Mach
 * Core Used:
 * Chaser Cobra, Chaser Spider, Chaser Bat (all are absorbed into Chaser Mach)
 * Tune Used:
 * Chaser Cobra (Chaser Muchi), Chaser Spider (Chaser Tsume), Chaser Bat (Chaser Yumiya) (all absorbed into Chaser Mach)

Errors

 * When changing into Chaser Mach, the close up shot of Chaser Mach shows that the left side of Chaser Mach is covered with Chaser's underarmor is slightly different than the preceding and aftershot before it.
 * When Chaser Mach does a 360 spin around Gold Drive, the camera angle of the shot shows the suit actor of Chaser Mach actually missing before cutting to an angle where it looked like it actually connected.
 * Before Go kills Banno, the Shingou-Ax announces "Matteroyo" before Go even hit the red Shingou Push Button.