Otome Game no Heroine de Saikyou Survival - Chapter 42

A teenager named Evan Mason was reincarnated into the magical world of Harry Potter and goes to school at Hogwarts!
With only his knowledge of the future and great talent for magic, he takes the path towards the top of the magic world, only to realize that ever step he took, changed everything!

- Description from Novelupdates

Wang Yi gets a key, opening a door in 2022 will lead to 1982, and opening a door in 1982 will return to 2022.

Two very different great eras appeared before him:

Abundant dietary protection, developed industrial products, miraculous medicines, and explosive information, this is 2022.

Simple folk customs, rich wild resources, scattered antiques, and treasures of the age, this is 1982.

Traveling between these two eras, Wang Yi didn’t think much of it, he just wanted to live a good life.

- Description from novelbuddy

When an unlucky, awkward virgin dies in the most humiliating way possible (you don’t wanna know), he wakes up not in heaven… but a mechanical construct powered by divine magics built for a single purpose: Sex.In a fantasy world cursed by a sexually frustrated demon queen, men can’t keep it up, women haven’t had a decent orgasm in centuries, and birth rates have plummeted harder than masculine egos. Society is teetering on the edge of population collapse—and the only thing standing between mass hysteria and sweaty salvation... is him.His new owners? A smoking-hot, elven herbwitch MILF and her fiery half-dwarf, half-elf genius daughter who created him as their latest “intimate invention.” After a magical screw-up gives him a soul (and an upgrade below the belt), he becomes the only pleasure unit capable of leveling-up his powers of pleasure, independent thought—and maybe... emotional connection?Now powered by aphrodisiacs, awkwardness, and sheer mechanical stamina, our hero must navigate lusty labs, intense moaning missions, and a society starving for satisfaction... all while trying to survive being “tested” and “reviewed” by every noblewoman, monster girl, and lonely tavern wench in the realm.------------------WARNING: May contain excessive thrusting, magical lubricant, seductive stat screens, and one very confused virgin trying to do the right thing! Reader Beware... and bring tissues.

Everyone believes Lin Zhao Xi’s a genius.

Only she knows she’s looking back on years of experience in math competitions as a basis to “cheat”.

Until one day, her idol quietly looks at her.

* * *

Time and space overlap, returning thrice.

— The past can change you.

- Description from Novelupdates