Sui Kamishiro possesses short, messy dark blue hair and striking blue eyes, accentuating a very fit and toned physique. She favors sporty outfits, primarily in blue and white, which complement her energetic nature while still allowing a distinctly feminine charm to surface.

Her personality is intensely lively and competitive, excelling at sports to a degree that leaves others struggling to match her pace. This athletic prowess is shadowed by a unique condition: an extreme allergic reaction to men that triggers an instinctive punch toward any male who makes physical contact. This trait, combined with her fitness and princely demeanor, has garnered her significant popularity among a female fanbase.

Sui was first encountered at a local swimming pool, where a manager and another individual reached a drowning child just before she could. In response, she challenged the manager to a rematch but was instead drawn into a sing-off with another person, which she lost. The ensuing argument led to the manager attempting to intervene and being punched by Sui. She later sent a formal letter challenging the manager to another performance rematch at the pool, an event she also lost.

After this second defeat, she revealed the origin of her man allergy: a past incident involving a boy who transferred to her class. He had defended a girl from a larger boy, becoming her role model and inspiring her to train herself to become like him. It was suggested that her hidden feelings for this boy might underlie the allergic reaction. Following this realization, she expressed a desire to develop into a proper woman and grew very close to another character, though her man allergy remains.

She is an active member of the swimming club and occupies a role in a subunit where she embodies the sporty, confident, and impulsively altruistic older sister figure.