To Love-Ru: Spoiler Route

Yuuki Rito’s life was supposed to be ordinary, until the night before everything began, he dreamed of a world where he was someone else, someone who had read every chapter, every panel, every tear-stained confession of To Love-Ru up to its final page. He woke up with no name, no face, no past, only perfect, unbreakable knowledge of the future. Now, on the morning an alien princess is destined to crash naked into his bathtub, Rito holds a notebook filled with every accident, every heartbreak, and every girl who will one day love him. He is still the same shy, stuttering, and sweet Rito the universe knows. But this time, he refuses to let a single flag go unraised, a single tear go unshed, or a single heart go unbroken. Armed with spoilers sharper than Yami’s blades, manga manuscripts that will reshape Shōnen Jump itself, and a Darkness overload that makes the King of Deviluke flinch, Rito will stumble, blush, and apologize his way straight into the one ending the canon never dared to draw: A galaxy-spanning wedding with Twenty Rings on his trembling fingers. This is the story of the boy who read the manga so none of the girls ever had to cry again. Welcome to the Spoiler Route, where the dense protagonist finally reads the room… and rewrites the entire script. — Description from novelcodex.org