|This article is about a/an episode in Engine Sentai Go-Onger.|
Partner Gunpei (相棒グンペイ Aibō Gunpei) is the twenty-eighth episode of Engine Sentai Go-Onger.
People begin disappearing mysteriously throughout the city, with Gunpei frantic of the event in spite of disappearances yielding no evidence of Gaiarc involvement until they find the guilty party, Manhole Banki. After the Savage Machine Beast escapes them, the Go-ongers get arrested by the police as suspects in the missing person’s case. Once at jail, the team is released by Gunpei's old partner, Detective Sakyo Kashiwagi, of the Tokyo Metropolitan Police Department, who is also investigating the case as well. After Gunpei explains the situation, Kashiwagi requests Gunpei to be his partner again to investigate the mystery of why Manhole Banki is abducting people, not admitting the culprit's identity. Using Gunpherd's nose to track down one of Manhole's recent victims, Manami, Gunpei and Kashiwagi make their way to the school she works, where Gunpei realized the Gaiark were targeting pen-spinners. Deciding to set up a trap with the Go-on Wings' aid, the Go-ongers disguise themselves to wait out Manhole Banki before he finally makes his move, with Gunpei abducted. After telling the Go-ongers, Kashiwagi admits that Gunpei is just like he was the day he left the police force after he first saw the Go-ongers. While this occurred, once learning the Gaiark's newest scheme to use the pen-spinners to power-up Kitaneidas' Destructive Sound Machine, Go-on Black frees the prisoners before fighting Manhole Banki, destroying the machine as the others arrive to defeat him with Super Highway Buster/Wing Booster combo. Kashiwagi arrives as Engine-Oh G9 battles the Industrial Revolutionized Manhole Banki, using Gunpherd to take out the manholes before scrapping the Savage Machine Beast. Kashiwagi later thanks Gunpei and Gunpherd for their help in solving the case, with Gunpei being picked on by his team once they learned that Gunpei was never a detective.
- Sosuke Esumi (江角 走輔 Esumi Sōsuke): Yasuhisa Furuhara (古原 靖久 Furuhara Yasuhisa)
- Renn Kousaka (香坂 連 Kōsaka Ren): Shinwa Kataoka (片岡 信和 Kataoka Shinwa)
- Saki Rouyama (楼山 早輝 Rōyama Saki): Rina Aizawa (逢沢 りな Aizawa Rina)
- Hant Jou (城 範人 Jō Hanto): Masahiro Usui (碓井 将大 Usui Masahiro)
- Gunpei Ishihara (石原 軍平 Ishihara Gunpei): Kenji Ebisawa (海老澤 健次 Ebisawa Kenji)
- Hiroto Sutou (須塔 大翔 Sutō Hiroto): Hidenori Tokuyama (徳山 秀典 Tokuyama Hidenori)
- Miu Sutou (須塔 美羽 Sutō Miu): Yumi Sugimoto (杉本 有美 Sugimoto Yumi)
- BOMPER (ボンパー Bonpā, Voice): Akiko Nakagawa (中川 亜紀子 Nakagawa Akiko)
- Engine Speedor (炎神スピードル Enjin Supīdoru, Voice): Daisuke Namikawa (浪川 大輔 Namikawa Daisuke)
- Engine Gunpherd (炎神ガンパード Enjin Ganpādo, Voice): Kenji Hamada (浜田 賢二 Hamada Kenji)
- Water Pollution Minister Kegalesia (害水大臣ケガレシア Gaisui Daijin Kegareshia): Nao Oikawa (及川 奈央 Oikawa Nao)
- Air Pollution Minister Kitaneidas (害気大臣キタネイダス Gaiki Daijin Kitaneidasu, Voice): Mitsuaki Madono (真殿 光昭 Madono Mitsuaki)
- Manhole Banki (マンホールバンキ Manhōru Banki, Voice): Kentarō Itō (伊藤 健太郎 Itō Kentarō)
- Sakyo Kashiwagi (柏木左京 Kashiwagi Sakyō): Tomohiko Imai (今井朋彦 Imai Tomohiko)
- Kiyoshi Shimazaki (島崎清 Shimazaki Kiyoshi): Masahiro Kawaura (川浦正大 Kawaura Masahiro)
- Haruko: Rie Tsuneyoshi (恒吉梨絵 Tsuneyoshi Rie)
- Manami: Miwa Hashiguchi (橋口未和 Hashiguchi Miwa)
- Police: Tetsuji Toshikura (利倉徹治 Toshikura Tetsuji)
- Detective: Masaru Ōbayashi (大林 勝 Ōbayashi Masaru)
- Child: Shutaro Maeda (前田秀太郎 Maeda Shutarō), Yuki Sato (佐藤勇輝 Satō Yūki)
- Go-On Red - Change Soul, Engine Soul #1, Blaster Soul
- Go-On Blue - Change Soul, Engine Soul #2, Blaster Soul
- Go-On Yellow - Change Soul, Engine Soul #3, Blaster Soul
- Go-On Green - Change Soul, Engine Soul #4, Engine Soul #6, Blaster Soul
- Go-On Black - Change Soul, Engine Soul #5, Engine Soul #6, Blaster Soul
- Go-On Gold - Change Soul, Engine Soul #7, Engine Soul #9, Blaster Soul
- Go-On Silver - Change Soul, Engine Soul #8, Engine Soul #9, Blaster Soul
- As part of Super Hero Time, this episode aired alongside Kamen Rider Kiva episode 30, Curtain Raising: Kiva's Identity.
- Engine Narrator: Engine Gunpherd
- Engine Eyecatch Race Winner: Engine Birca ("I did it, amigo!")
- Go-On Seminar: What was Gunpei's nickname when he was a "detective"?
- Answer: The "Cool" Detective (though as pointed out, he never became a detective anyway).
Engine Sentai Go-Onger DVD Volume 7 features episodes 25-28.
The Blu-ray release of Engine Sentai Go-Onger Volume 2 features episodes 17-33.