Akiko Shimizu is a classmate at Kouchi Outemae High School. While not the student-body president, she wields significant influence among the female students, advocating against gossip to maintain class unity and earning respect for her efforts to keep the girls cohesive. Her surname means "clear water" or "pure water," and her given name combines the characters for "bright" and "child." Initially, Akiko strongly dislikes Rikako Muto due to Rikako's detached attitude and refusal to participate in group activities, especially during cultural festival preparations. She confronts Rikako about this lack of involvement, demonstrating her emphasis on collective responsibility. Later, Akiko witnesses another female student attempt to physically attack Rikako, believing Rikako flirted with her boyfriend. Akiko intervenes verbally to restrain the aggressor but does not actively defend Rikako. After high school, Akiko's perspective shifts. She encounters Rikako in Obiyamachi and initiates a conversation, moving past their previous conflicts. At a class reunion, she informs Taku Morisaki and Yutaka Matsuno about this meeting, explaining Rikako's absence is due to attending a women's college in Tokyo. During this reunion, Akiko reflects on her high school behavior, acknowledging her own immaturity and that of her peers during that time, recognizing the world extends far beyond the limited view she held as a teenager.