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.