25-sai Shojo 7-sai Toshishita no Danshi Koukousei to Dousei Shimasu!?

A 25-year-old woman who writes relationship advice columns is actually completely inexperienced with romantic or physical relationships. She is offered a job to write a realistic, adult-oriented romance novel but becomes overwhelmed and drinks heavily at a bar. The next day, she wakes up to find the bartender from the night before in her home. He reveals that he is a high school student. The two will now live together in secret as she begins to learn about adult intimacy from him.