10-nen Shitenai Sudachi-san

Chikako Sugata is a 32-year-old "sudachi" (a sour lemon), who spent her twenties in the countryside without any romantic relationships. She finally decided to move to Tokyo to rediscover her youth! To have one last memorable occasion before leaving, she went to a bar at midnight and had a one-night stand with a man from her home town...!? (Source: Akita Shoten, translated)