Takenori is a major fan of Dating Sims. One day, he receives a strange eMail that tells him he can be the main character and asks him to insert the source material for his new world.
Takenori inserts his favorite Dating Sim "Eternal Innocence" and after strange things he mistakens for a dream, wakes up - to find that all the heroines from Eternal Innocence have come to life in his usual surroundings!

Aramiya Seiichi is an ordinary high school... eroge otaku who's given up all hope on girls in the 3D world due to a certain incident. One day, after he's bought a bunch of new material in consequence of experiencing the frustration of a perfect eroge character turning out to be "used goods," he encounters a delinquent-like-looking girl being about to get raped by a bunch of guys. By mere chance, he rescues her. Days later, when school starts again, it turns out to have been his classmate, Ayame, a feared delinquent girl who's got all kind of rumors about her—especially that she's "used goods." And it appears that she's set on becoming his ideal girl to make him fall for her.

(Source: Novel Updates)