Hisui is a quiet, gentle maid in Tsukihime who works at the Tohno household alongside her twin sister, Kohaku. She is reserved, polite, and often appears expressionless, but she is deeply caring and attentive to those around her. In the story, she serves as one of Shiki Tohno’s routes and is closely tied to the mysteries and emotional tensions within the mansion. Her calm demeanor and subtle inner struggles make her an important character in the series.