From the time she was in high school, Hatsu assisted her older sister Kai Yukiko, a successful manga artist and member of the Post Year 24 Group. After graduating high school, she began working for a printing company in Kanazawa City, but she soon quit in order to become a full-time assistant to her sister. She also began to assist other professional artists, most notably Hagio Moto.

Throughout this period, Hatsu was creating doujinshi with her friend Sakata Yasuko (who also went on to become a prominent professional manga artist and a member of the Post Year 24 Group), and sometime around 1980, the two of them coined the term yaoi. In 1980, Yukiko Kai died of stomach cancer at the age of 26. The following year, Hatsu made her professional debut in the magazine ALLAN with the short story "Nami no Banka".

Hatsu served as an adjunct instructor at Kyoto Seika University until retiring in 2005 due to health issues.