Hinako Ayakawa is Shungo Ninomiya's classmate in Class 1-A, holding undisputed leadership and significant popularity at school. She persistently subjects Shungo to sexual harassment—restraining, binding, and pressuring him—openly labeling these actions as harassment. Her invasive behavior escalates with friends' assistance, ensuring Shungo experiences no respite. Initially viewing transfer student Mayu Tsukimura as a rival for Shungo's attention, Hinako shifts her stance after a joint shopping trip, rapidly forming a friendship. However, she extends her invasive conduct to Mayu, displaying particular interest in Mayu's larger bust size.

Hinako exhibits an open-hearted, confident personality, actively seeking social interaction and expressing thoughts candidly without pretense. Though generally cheerful, dissatisfaction with her own smaller bust size affects her mood. She shares Mayu's enthusiasm for manga, including Boys' Love genres, willingly offering her collection to Mayu. Mayu reacts with visible blushing and apparent curiosity, especially during scenes where Hinako reads BL manga near a sleeping Shungo. Hinako participates in group activities, such as a ramen-making endeavor where she wears both an apron and swimsuit in the kitchen.