|Chapter 1||Next →|
|Teppei Sugihara, Bossun, Himeko, Switch, Jōgasaki, Yumi, Masatoshi Kosaka|
Shortly after transferring to Kaimei High School, Teppei comes to the Sket Dan covered in paint and asks for their help in catching the one responsible, who they dub "Paint-Mask." The trio leap into action, going around and questioning students in the area of the incident. They learn that a troublemaker named Jōgasaki had been cleaning walls nearby, and decide to tail him. After Bossun is targeted by Paint-Mask and the group return to the clubroom to compare notes, Bossun utilizes his concentration mode to discern the truth behind the incident.
Bossun sets himself in an open area as bait, and when Paint-Mask appears, Himeko catches him. Bossun reveals that it had been Teppei all along, and Switch adds what he had discovered about the relationship between Teppei and the troublemaker Jōgasaki: the latter had bullied the former in primary school. When Teppei despairs at his inability to stand up for himself if he wants to have a peaceful school life, Bossun grabs the paint bucket and dumps it over his own head. He declares that the Sket Dan will always help out a friend in need, no matter what they need to do to that end. The trio then locate Jōgasaki, who had been watching the entire time, and Himeko beats him senseless.
Some time later, the Sket Dan mourn Teppei having joined the basketball club rather than their own, then head off on a request from the school janitor. One of Teppei's teammates asks him about the wristband he's wearing, which he received from the Sket Dan members, and he says it is a proof of friendship.