Sayaka Sumino

Sayaka is Akuru and Yoshiko's classmate who ends up becoming friends with the two. She is level-headed and assumes the straight-man role, often moderating interactions between Yoshiko and others.

Sayaka is kind and worries about being boring. She is very sensitive, especially when others point out her small chest, which appears slightly small, even after she pads it. She sometimes loses her patience. Most people acknowledge her kind aura and the binding and relaxing effect it has on everyone.

(Source: Aho-Girl Wikia)