Okita asks the Yorozuya to investigate an underground fighting ring, but the gang finds out that there's more to one of the members than it seems.
The Yorozuya is watching a women wrestling match, in which Terakado Tsuu participates. After Kagura enters the ring, Gintoki and Shinpachi are about to leave, when they spot Sougo amongst the viewers. Sougo takes the gang to an underground fighting ring called Rengokukan. In this arena real death matches take place including gambling. The Shinsengumi cannot interfere as certain political figures are involved behind the scenes. Before they leave, Okita asks them to spy on Kidomaru, Rengokukan's strongest fighter.
They follow him to an abandoned house, where lots of orphan kids live. It looks like Kidomaru is looking after these kids. In the past he was a skilled swordsman called "Killer". Before he was executed, the Tendoshu freed him and forced him to participate in their illegal matches. At the same time Sougo is beating some small fries of the illegal organisation, but he is soon spotted by Hijikata. Hijikata and Sougo treat Gintoki to inform him that he should not be involved anymore. At the same night, Shinpachi and Kagura are sent to watch out for Kidomaru at his house. However, he informs them that he is about to leave with his children. Shortly after, a group of assassins sent by the Tendoshu arrives to eliminate Kidomaru. Shinpachi and Kagura stay to fight them, while Kidomaru escapes. Unfortunately, as he is about to escape, an assassin, who will become the next king of Rengokukan, Onijishi, stabs Kidomaru with a spear, which ultimately kills him.
Back at Odd Jobs Gin, Sougo talks with the Yorozuya, when suddenly Kidomaru's orphan children enter the scene to beg Gintoki to avenge their Sensei. Gintoki, along with Shinpachi, Kagura and Sougo decide to face the Tendoshu in the arena, much to Hijikata's surprise. Gintoki enters the arena to face Onijishi, who is rampaging against some pitted samurais. He wears Kidomaru's demon mask, which results in getting mistaken for the real thing. After a fierce battle, Onijishi manages to land a hit with his giant club to Gintoki. However, Gin has managed to partially block the hit with his wooden sword and with his next move he launches Onijishi KO'ing him. As the Tendoshu forces enter the arena, Kagura, Shinpachi, Sougo enter to back him up, followed shortly by Shinsengumi members.
The real Boss behind the bloody matches gets away quickly. Having destroyed the arena, the group sits on a bridge, with Gintoki destroying Kidomaru's mask, as "he won't be needing it anymore in heaven".
- Sakata Gintoki
- Shimura Shinpachi
- Terakado Tsuu (cameo)
- Hachibei Takaya (cameo)
- Okita Sougo
- Hijikata Toushirou
- Kondou Isao (mentioned)
- Onijishi (debut)
- Oshou Doushin (debut)
- When Kagura enters the ring, she calls herself Antonio Kagura. This is a reference to the famous Japanese wrestler Antonio Inoki
- When Gintoki spies on Kidomaru's house, he gets spotted and gets a finger attack in his rear end. This could be a reference to Naruto, as this move is commonly used there.
- This is the first episode Hijikata and Sougo are appear without Kondou in this episode.