Ichika Watanuki, 25, is the eldest of three sisters living in Tokyo's Monzen-Nakacho neighborhood after their parents' deaths. Their mother died during their early childhood, and their father passed away approximately one year before the main events, leaving the sisters to inherit the family home. This history of loss defines Ichika's responsibilities and emotional core.

She balances a mature, responsible demeanor as the family leader with traits of an earnest airhead—prone to worry and occasional absentmindedness. Her workaholic nature prioritizes career ambitions over personal connections, leading her to declare "work over love." Despite this stance, she lacks romantic experience and stumbles in interactions with men, frequently turning to her sister Futaba for guidance.

Professionally, Ichika pursues voice acting, a dream inspired by childhood anime that provided solace after her mother's death. She sustains herself through part-time jobs while striving to offer others the same emotional refuge animation once gave her.

Her daily life involves navigating challenges with sisters Futaba (23) and Mitsuki (20). Their interactions blend supportive bonds and conflicts, tested by events ranging from humorous mishaps to emotionally charged moments—such as their troubled attempt to commemorate their father's first anniversary. These experiences continually reshape their dynamic.

Ichika's growth emerges through juggling family duties, career goals, and self-discovery. Her journey involves reconciling her responsible facade with underlying vulnerabilities. Participation in family conflicts and resolutions fosters gradual maturation in her relationships and self-awareness.