Apparently, she had gone back in time to manipulate the DNA of a "megaplayboy," who eventually had over 100 children, in order to help fight overpopulation.
She claims the "megaplayboy" is the protagonist, much to his disbelief.
She realizes that she has made a critical mistake, and must now kill the protagonist.
However, the hero is able to distract her and knock her unconscious, and moves her to the basement.
The game is structured into days, with 100 energy points that can be invested into different activities.
These activities can be used to improve various stats.
Meanwhile, on the way to Fight Club, the hero encounters Ryuji.
Ryuji wants the protagonist to avoid all of the girls in town, who he feels are rightfully his.
Three weeks later, the girl from the future returns.
It is now his duty to take care of her on a daily basis.