Kasumi Shikouin is a schoolgirl with a longstanding childhood friendship with Tsutomu Tachibana. She possesses the supernatural ability to see others' true emotions, which she deliberately suppresses using specialized glasses, reflecting her desire for privacy and emotional distance. Intelligent and typically composed, she participates in student council activities at Makoto Okano's school. However, interactions with Tsutomu frequently test her composure, especially when he flirts with others, visibly irritating her. She often engineers situations requiring his help, like insisting he give her bicycle rides to school, as a way to spend time with him. These actions subtly hint at deeper, unexpressed romantic feelings towards Tsutomu that he consistently fails to notice. Her routines include buying tea leaves from Hikari Tsukishiro's shop. Kasumi remains consistent in her reliance on Tsutomu and her concealed emotional investment in their relationship across documented adaptations.