Just because of a book, the heroines in each volume travel to different eras and have different stories with legendary historical figures. When they time travel, their present-day bodies disappear until they return. When they travel to different time and space, modern time will stop and people will not remember their existence.
However, their time travel will not change history. However, when they travel through time, a guide will appear. (This article does not conform to history. If there is any similarity, I would be honored.)