Marina Mochizuki is a high school student and close friend of Ichika Mizuhara. Her blonde hair, blue eyes, and notably well-endowed physique frequently draw attention from male characters, irritating peers like Ichika, though she neither seeks this attention nor holds responsibility for others' reactions. Marina exhibits a reasonable and calm personality, serving as the straight man in comedic group dynamics with grounded or sarcastic responses to eccentric behavior. She maintains a composed, gentle demeanor but displays poor taste in men. Her familial background includes a half-brother, Souichirou Fuji, who is half-Russian, blonde, fluent in English and Japanese, and an otaku obsessed with gal games. Marina harbors a brother complex, showing affectionate or overly invested interest in his activities. She shares strong bonds with friends, regularly participating in group gatherings at Ichika’s house or trips to locations like public swimming pools. Her interactions consistently reinforce her role as a supportive yet normalizing presence within the ensemble.