Ayumu Shiiba is a middle school girl, and she is amidst studying for high school entrance exams. Ayumu is always struggling in tests, and she gets help from her best friend Shii-chan, who is always the top score taker in class. The two aim to go to the same high school together, and they study hard. Ayumu eventually beats Shii-chan in test scores, and it leads Shii-chan to fall into despair. In order to avoid hurting her best friend, Ayumu gradually lies about her superior test scores from Shii-chan. On the day the tests results are announced, Ayumu is shocked to discover that she passed into the high school of her choice, and Shii-chan did not. Shii-chan is outraged from the results, accusing Ayumu of betrayal and being reliant too much. The two best friends' relationship has been destroyed. Ayumu tries to alleviate Shii-chan's pain by cutting herself in the wrist. Ayumu cuts herself multiple times as a form of apology to Shii-chan. She begins to believe that the pains from the cuts are the only solace from all the agony she has been through. As the new school year starts, Ayumu carries an exacto-knife in her pocket for comfort.
As the days go by, Ayumu has finally made a new friend at her new school, Manami Anzai. Manami is a cheery girl, and she talks mostly about her boyfriend. Manami's sometimes manipulative and unpredictable behavior flutters Ayumu. Manami seems to let Ayumu into her other group of friends, but Ayumu still has a hard time making good friends because she is afraid of hurting them like Shii-chan. One day, Ayumu makes plans to meet with Manami, and Ayumu finds that Manami had broken up with her boyfriend. Manami is shaken up, and she tries to jump in front of a train to kill herself. Ayumi saves her, but Manami seems to be more angry than thankful for being saved.