“High School Boys and the Holy Night” is the 31st chapter of the manga.
The main trio narrowly escape a construction block thrown at them by Yoshitake's older sister. They seem scared for their lives while she seems to be hunting them with a violent rage. In a flashback, it is revealed that the day is Christmas Eve (A traditional romantic holiday in Japan) and Hidenori was at Yoshitake’s house. He remarked casually to Yoshitake’s sister that she seemed to be home even though it was Christmas, which she took extremely badly.
In the present, Hidenori says he didn’t mean it that way and Yoshitake dismisses Tadakuni’s misgivings about his sister being a kind person, adding that she was the ringleader of the group that took off Motoharu’s goatee. Yoshitake is then felled by his sister with a flying kick to the head, startling the others.
Tadakuni is next, as he is caught from behind and thrown over some nearby rails. Hidenori flees in fear with his pursuer hot on his heels. She loses him near a crowded area and slows to a halt. Wandering about, she sees all the couples around her, and feels embarrassed at being alone. Disgraced, she buries her face in her hands. Suddenly, a hand touches her shoulder.
It turns out to be Hidenori, who noticed her situation and wants to help out. He says the least he could do at this time was to be with her. She smiles, as if reaching for his hand, before punching him in the face with force enough to shatter his glasses, asking him indignantly if he was stupid or something.
In order of appearance: