Ichika Watanuki, the 25-year-old eldest sister of the Watanuki family, lives with her two younger sisters in Tokyo's Monzen-Nakacho district. The sisters reside together in their inherited family home following the deaths of their parents; their mother passed away during their early childhood, and their father died roughly one year before the main events.

After her mother's death, Ichika sought emotional refuge in anime, which directly fueled her career ambition to become a voice actress. She embodies maturity and responsibility but is also a workaholic, frequently prioritizing her part-time jobs and professional aspirations over social life and romantic relationships. This dedication stems from her drive to achieve stability and independence for herself and her sisters.

By the second season, Ichika progresses toward her voice acting dream, securing occasional work in the field while maintaining part-time employment. She adapts to shifts in the family dynamic, including her middle sister moving out after marriage, though they remain closely connected. The sisters continue to frequent Masako, a local karaoke bar that served as a second home after their mother's passing, reinforcing their support network.

Throughout the series, Ichika fulfills her role as the eldest sister by providing stability and emotional support during various challenges. This underscores her resilience and unwavering commitment to family bonds amidst personal and collective hardships.