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Upon visiting her friend, Run, to tell her she managed to get into her high school, Tooru finds her in a compromising position with one of her classmates, Yūko, who Tooru takes an instant disliking to. School soon begins, with Tooru showing hostility to anyone who gets too close to Run, and Yūko and their other friend, Nagi, making sure Run doesn't hurt herself with her aloofness. After school, Tooru admits she feels lonely being in a separate class from Run, but Run assures her that nothing's changed between them.

Run gets into a little trouble when she forgets to put on her underwear in the morning. Yūko goes into a little panic when Run collapses, though it turns out to be just a bit of sleep deprivation. After having to deal with heavy rain, the girls spend the evening at Nagi's house to dry off. While Run and Nagi take a bath, Tooru forces Yūko to sit through a scary movie before continuing to tease her during their bath time. A little while later, the girls leave with some umbrellas they borrowed, but soon return after Yūko gets herself dirty again.

In her first year class, a classmate named Yutaka becomes overly friendly towards Tooru, which bothers her a bit. Meanwhile, a new health teacher, Mr. Satō, becomes attracted towards Run due to her forehead, which naturally bothers Tooru. It is later revealed that Satō is physically weak himself. As Yutaka becomes increasingly clingy to Tooru, her friend Miho tries to keep her in check, though this admittedly makes Tooru feel lonely.

As the students clean the school up, Miho gets to know Tooru, much to Yutaka's chagrin, while the other girls have some fun cleaning the pool. Later, Nagi becomes concerned that she's gaining weight and goes on a diet, but is later convinced that she shouldn't force herself to do so.

After noticing the first years hanging around the pool, Run suggests a trip to the beach for summer vacation. Yūko and Nagi go swimsuit shopping, while Run gives Tooru her swimsuit from elementary school, do to Tooru's small stature. They soon arrive at the beach, where they have fun playing in the sea and sand.

Run ends up giving Tooru an undesirable haircut, but manages to fix it into something she appreciates. Tooru has trouble dealing with her erratic teachers while Yuko mistakes Yutaka's way of dusting out her neckerchief as a cry for help. When Yuko forgets a form she needs to fill in at school, the gang decide to sneak into the school at night to retrieve it, as well as do some exploring. As Nagi and Yuko go to the bathroom, they spot a strange glow outside, which they later discover to be Mr. Satō who then collapses, forcing the others to carry him to the nurse's office. At the end of the day, Yuko still forgets to collect her form.