A 13 year old girl who moves into the Kanemasa mansion atop the hill with her family. She has a rare genetic disorder known as SLE, which leads her to stay inside her home during the day and only come out at night. She and her family are fans of the essays and novels written by Seishin Muroi, and is the reason they moved to Sotoba. Sunako dislikes people calling her name with the honorific "chan".