Storyline & Synopsis of 9 Border

It follows the story of Oba Nana, a middle child among three sisters who is 29 years old, single, and works hard at her job. She receives a promotion at her job to become the youngest assistant manager, but she feels anxious due to her friends getting married and having children. Her two sisters are 39-year-old Narusawa Mutsuki and 19-year-old Oba Hatsumi.

Narusawa Mutsuki works as a certified accountant. She is currently separated from her husband due to her husband's infidelity. Oba Hatsumi feels uneasy with people her age who have their own life goals and pursue their goals. In order to comfort her feelings, she meets a man from a dating app.