Fumitsuki Nanakorobi, whose surname meaning "seven turnings" reflects her persistence, is class president at Chitose Hitotose's school. She achieves excellent academic marks and holds authority within the classroom. Physically, she has black hair reaching her chest, green eyes, stands 155 cm tall, and typically wears glasses. Her personality blends diligence with aggressive tendencies; she often punches classmates or Chitose forcefully to silence disruptions or express frustration, typically in a comical manner.

Persistent romantic feelings for Chitose, who remains oblivious for much of the series, drive a central aspect of her character. She continuously attempts to win his affection, employing methods ranging from attentive concern to physically confrontational interactions. Her behavior includes elements of stalking, opportunistic advances, and tsundere-like switches between harshness and vulnerability, such as taking advantage of an unconscious Chitose falling onto her, resulting in an accidental kiss.

Her development culminates in the final season with an open confession of her feelings to Chitose, marking a significant shift from earlier indirect approaches. She engages in rivalry with Kanna Togakushi, another character vying for Chitose's attention, highlighting her competitive streak in romantic matters. Despite her authoritative role, she displays moments of tenderness, including lap pillow scenes where Chitose rests his head on her lap.