In the year 2022, Kazamidori Aki works at the Time Travel Research Facility with her assistant Miyama. They use a technology called Aston that has scanned every detail of the city for the past twenty years and recreates the past exactly as it appeared into a client's mind. This process called the In-Brain time travel allows the user to visit his past. But because it is only in their mind, they are unable to change anything in the present so no time paradoxes occur. Aki uses her services to help those who made mistakes in their past and help them change their ways. There is something odd about Aki's past that makes her very unique and she has to deal with the skeletons in her closet.

(Source: MangaHelpers)