A cheerful high school girl who also suffers from insomnia like Ganta. She first discovered the abandoned observatory and made it her sleeping haven, until Ganta came along.

Spoiler

As she and Ganta became closer, she shared to him that she has congenital heart disease which requires monthly examinations, frequent hospitalization, and even surgeries. She was the only other member of the Astronomy Club in her first year, and became the vice-president later in the winter of the same year.

Spoiler

She started dating Ganta after his confession at the end of their club trip. Initially, she aimed for a university within Ishikawa Prefecture, until she managed to convince her mother to allow her to try for a university in Osaka.