Shisui Tsuchimikado, the elder daughter of the Tsuchimikado family and sister to Kuon Tsuchimikado, possesses strikingly long white hair extending past her hips. Her eyes remain unseen in available references. Identified as female and of Japanese nationality, she falls into a magically induced coma prior to the series' events. This coma is initially blamed on a curse by Suishō Hakamada, prompting Kuon to enter the Granbelm tournament seeking a cure for her sister.

Later revelations expose Shisui's orchestration of her own condition: she tricked Suishō into consuming a fragment of her soul. This deliberate sacrifice transferred a portion of Shisui's magical power to Kuon, strengthening her sister's chances in Granbelm. Kuon uncovers this truth during the tournament.

Shisui exhibits a protective and affectionate bond with Kuon, demonstrated through gestures like nearly kissing her when Kuon cried and hugging her warmly, highlighting their emotionally supportive relationship.