Sumire Suō is a first-year student at Warabi Seinan High School and a key member of the girls' soccer team. She has white hair and dark blue eyes, and is typically seen in her school uniform: a plain white dress shirt, green jacket, blue plaid skirt, and a blue tie.

Sumire carries herself with a cool and composed demeanor, rarely showing emotion to those outside her team. Her speech is often blunt and can be rude, such as when she openly insulted a teammate for a mistake during practice. She holds a particular disdain for arrogance and finds supreme happiness in publicly humbling those who look down on her. Fierce rivalries drive her, and she does not hesitate to employ tactics like blackmail when necessary, as seen during negotiations for a futsal tournament.

Her soccer career began in middle school, where she served as captain of the Kawaguchi Middle School team. A match involving Eriko Tase first drew her interest to Warabi High, as Tase’s effort resonated deeply with her. A significant loss to Todakita Middle School before high school left a lasting mark, fueling her determined mindset.

On the field, Sumire is recognized for her exceptional speed. She is a left-footed player who actively avoids using her right foot. Though her talent was somewhat stifled in middle school by a team that struggled to match her abilities, she finds a more fitting environment at Warabi High.

Her relationships with teammates are layered. She initially viewed Midori Soshizaki as a rival and a thorn in her side from their middle school tournaments, though her impression softened when Midori suggested they attend the same high school so Sumire wouldn’t have to play alone. She was first impressed by Nozomi Onda’s effort but grew frustrated by her lackadaisical practice attitude. Over time, Sumire acknowledges growing fond of the entire team. Her rivalry with Mao Tsukuda of Kunogi Academy is especially intense, characterized by mutual insults and strategic confrontations, including an instance where Sumire blackmailed Tsukuda to secure her cooperation.

After a practice match loss to Kunogi Academy, Sumire became determined to defeat them someday. She also participated in a futsal tournament to help raise funds for new team kits, performing well during the Saitama preliminaries.

Key quotes include her telling Eriko Tase, "We're the same. You're just like me," reflecting her recognition of a kindred spirit. To Mao Tsukuda, she once said, "Your ferry fee. Do you have it? Are you ready to be sent to hell?"—a statement emblematic of her competitive and confrontational nature.

Throughout her development, Sumire evolves from a solitary talent focused on individual performance to a player who increasingly values teamwork, finding a sense of belonging and shared purpose with the Warabi team.