MC is your seemingly average highschool boy who just happens to lead a life frought with inexplicable hijinx due to outside forces. One day he finds a light novel left behind on his desk and decides to take it with him and give it a read. To his surprise, he finds himself relating so very much with the main character and goes out to get the rest of the series to see where things go.
He enjoys the relatively new novels at first since they help him come to terms with similar events in his past but by the 3rd book he can't help but find it unnerving just how much of the story overlaps with his life. it then gets absolutely disturbing when he gets to a particular scene in the book after that is basically a line for line biography of a very private moment he had just only last year.
He looks further into the books and notices that the 4th book came out just a few months after the event happened to him and that online sources has it that the author is allegedly still in highschool. He figures that one of his classmates must be using him as their inspiration and goes about trying to lure out who that may be. Naturally he causes a stir with his suspiscions and antics but by the end of the week he difinitively concludes it's not one of his classmates.
That's when he gets called to the teacher's room to answer for the nuisances he's caused. He gets there only to find it's just him and his maths teacher in the room. She cooly tells him to have a seat and he expects her to grill him on his outburst earlier during the day in class but instead she apologizes for the confusion and admits to being the author of those books.
He's taken aback by this, especially since he has a thing for her, and is even more taken aback by it when she offers to have relations with him stating her awareness of how he feels about her. The catch however is that he must wait till after he graduates and she finishes up her novel series. Till then he has to put up with her stalking and help her make her series a success by giving her more material to work with. With one and a half years to go till that offer becomes legally sound, how will this hormonally charged young man put up with the antics his strangely virile teacher put him through?
The teacher gets him to go along with it and he'll be exposed to hidden sides of his life hinted at in the novels. He'll gradually gets put off by it until her "plot direction" consultations with him actually do help him resolve an important personal issue he'd been avoiding.
After that, they'll get involved with the side characters and resolve their subplots under the pretext of making the novel stories even better making him and their relationship grow. They'll confide in each other and be more frank as time goes on but the solitary guarded front she rarely puts down will frustrate him.
She'll hurt him by publishing a critical and sensitive moment differently from what actually happened in a way that he strongly opposes. It creates a rift between them but this leads to him getting to see her at a low vulnerable point. They don't quite get over it but do try to put it behind them in the short term and this spurs character growth for the teacher as he begins doing stuff to help her with her issues the way she helped him.
Eventually she stops using MC's life story as a crutch and the novels diverge from it so she can write a more "pleasing" finale instead of tracing out the mature low key resolutions his reality has been taking. She actually does it to avoid hurting him but he pushes her to give it their best even if he though he knows it'll open cans of worms for him.
The series finishes on a bittersweet but highly rated note and their relationship and public interactions go cold due to how bad things look for them. They don't really talk to each other anymore until his graduation where the teacher goes to meet with him for one last consultation. She almost loses it at the prospect of letting yet another person walk away from her but he revises their bad end and insists on working together on their after story.