Banri Shiunji is the eldest daughter of the seven Shiunji siblings and serves as a central emotional anchor within the family. At nineteen years old, she is the only one of the children who has already moved on to university, where she is a first-year student enrolled in a prestigious program with the aspiration of becoming a nurse. Her birthday falls on January 21st. Notably, Banri was four years old when she was adopted into the Shiunji family, and it is hinted that she may retain some faint memories of her life before that time.

In terms of appearance, Banri is the second tallest of the siblings, standing only slightly shorter than her younger brother Arata. She has purple eyes and strawberry blonde hair styled into a bob, with a distinctive longer chunk on her left side that reaches past her collarbones, secured with a ponytail cuff. The right side of her hair is typically brushed behind her ear to reveal a gold dangle earring. Her fashion sense leans toward skirts and fashionable tops, and she is almost always seen wearing a necklace with a purple centerpiece.

Personality-wise, Banri is characterized as both cheerful and mature, often acting as the person who calms everyone down and helps identify people's feelings. She appears very satisfied with the direction of her life and has been described as both motherly and responsible, yet sometimes childish, particularly in her interactions with Arata. She has a habit of teasing him and acting coy in public, which leads to his embarrassment and her amusement. This playful nature is balanced by a deep sense of duty, as she has stated a resolve to protect her siblings with her very life, a conviction she formed upon realizing she was to be the eldest daughter of the Shiunji family.

Banri's primary motivation stems from her role as the eldest sibling. She feels a strong sense of responsibility for the well-being of her younger brothers and sisters and is willing to go to great lengths to ensure their happiness. This drive is also reflected in her academic and career goals, as her desire to become a nurse is rooted in a wish to care for and comfort people. In her university life, she is a member of the volunteer club and is said to be the most popular girl on campus, as well as within the fan club for the Shiunji sisters.

Within the story's dynamic, Banri serves as a key figure of stability. When the siblings discover that they are not related by blood, the family dynamic shifts dramatically, and complicated feelings begin to surface among them. During these times of rising tension, Banri's calm and mature personality often makes her the voice of reason. However, her relationship with Arata is particularly notable; despite her composed exterior, her interactions with him frequently blur the line between sisterly affection and flirtation, creating moments of confusion for him as he struggles with the revelation of their lack of blood relation. Even so, she remains a genuine source of emotional support for him, a role she has played since childhood when she would protect him from their other sisters who enjoyed picking on him and their brother Shion.

Regarding development, Banri is defined by her acceptance of her position in the family and her proactive decision to embrace it. Her background as an adoptee shapes her determination to protect the bonds she has formed. Throughout the story, she navigates the shifting dynamics not with confusion, but with a composed awareness, often being the one to understand people's feelings before they fully articulate them.

As for notable abilities, Banri is the sibling who cooks the most, taking on a nurturing role within the household. She is also the only one of the seven children who can drive, though she is nervous doing so due to a lack of practice. Furthermore, her status as the record-holder for the most romantic confessions received at the high school she attended with Arata speaks to her widespread popularity and charm.