Koko Tsukishima

Koko is the student of Kazemi affiliated junior high class 3-3, a childhood friend of Yoshiyuki and Nanaka. In the first season of the anime, she confesses her feelings for Yoshiyuki, which he accepts and they start dating, but later on in the first season, she breaks up with Yoshiyuki after coming to light that Yoshiyuki has been spending too much time on others, particularly Minatsu. Koko felt left out as a result and develop feelings of insecurities due to Yoshiyuki's insensitivity to the her feelings of loneliness. Koko is shown to be weak and cries frequently when she was young. Only after much persuasion from Yoshiyuki, does she smiles.

Koko also has a forgiving personality as shown when she has a quarrel with Yoshiyuki when they were young but forgives Yoshiyuki after he apologized. In the second season, she develops to become a more confident individual but still holds signs of weakness in her falling sick due to unknown reasons just before the puppet show where she is stated to play the female character.