For not raising his hand when asked, Haruki is called out by Akechi to stay behind after class. When they're alone, Haruki calls his teacher out for supposedly patronizing him when he's supposedly matured, and asks him why they keep up a barrier as teacher and student when they were friends before. Akechi regularly deflects the question, and questions why Haruki always puts up a tough front whenever they get in close proximity. This happens multiple times, though Haruki never relents and never raises his hand, tired of the gap between them.
Watching Haruki hang out with his friends, Saku gets flashbacks to his own time in high school when he hung out with Haruki's brother, Chiaki. He has visions of a beach day, water rushing up, Haruki as a child crying by a bedside, and Akechi himself looking distraught; all references to Chiaki's death, all but stating that they don't talk much anymore because of guilt that welled up from the incident.
When roll call happens again and Akechi asks if everyone likes their teacher and class, he finally realizes that he's the only one not satisfied. It cuts back to the argument in detention with Haruki finally breaking through to Akechi, offering to start on a fresh step so they can go back to their old relationship.