Tomoka Fusano is a 21-year-old woman with ochre hair, brown eyes, standing 1.61 meters tall, weighing 49 kilograms, and possessing a slender figure with measurements of 92-57-86. Her personality is open-hearted, lively, and notably self-confident, presenting a contrast to her sister. She shares a significant childhood history with her neighbor, Wataru. Following a period of separation, she quickly rekindles a close friendship upon their reunion. Tomoka dedicates substantial personal time to serving as Wataru's private tutor, sacrificing much of her leisure to support his academic progress.

Through their sustained and natural proximity during these tutoring sessions, Tomoka develops romantic feelings for Wataru that exceed friendship. True to her forthright nature, she openly acknowledges these emotions and actively pursues him in an unambiguous manner. She does this fully aware that her sister, Fumie, also harbors deep affection for Wataru. Typically, this situation could cause tension, but due to the exceptionally close bond between Tomoka and Fumie, they initially perceive no major issue and jointly decide to care for Wataru together.

Despite her generally confident personality, Tomoka expresses dissatisfaction with her breast size, considering it somewhat small, a concern described as objectively unfounded. She views her sister's larger bust with a degree of envy.