Festival of Thornies (S05E45)

Tetsunosuke is tasked with delivering a letter for Hijikata, but during his mission, he gets captured by the radical Joi Check It Out gang. Although he had disguised himself to infiltrate the group, they soon uncover his ties to the police. Taken hostage, he becomes a bargaining chip against the Shinsengumi and Mimawarigumi. Meanwhile, the Mimawarigumi remains indifferent to Tetsunosuke's fate and schemes to blame the Shinsengumi instead. Upon discovering Isaburo's intentions, Hijikata and the others are furious, leading to an all-out confrontation between the Shinsengumi and Mimawarigumi.