Senou Ai is a high school student distinguished by her short blond hair, brown eyes, and pale complexion, typically seen wearing a skirt. Her carefree and naive personality leads her to trust others easily, a trait that often leaves her vulnerable to deception. Despite being an absolute klutz with notably poor coordination—described as slower than "a snail going uphill" in races—she approaches tasks with a hardworking attitude, consistently dedicating 110% effort without shortcuts. Frequent dizzy spells send her regularly to the school nurse's office.

Her background includes losing her mother at a young age, an event that forced her into early self-sufficiency in household management while her family runs a fish shop. Deeply emotional, she readily swings between laughter, anger, and tears. As the protagonist's childhood friend, she belongs to his close social circle and participates in school sports club activities, though her role is confined to spectating due to her physical clumsiness. Her trusting nature continues to make her susceptible to exploitation.