Bofuri (The Strongest Shield Of Tensura) - Chapter 51 - Fifty One

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

A modern-day antihero, who was infamous for his devious acts, dies in an explosion meant to take down a powerful criminal syndicate. Waking up in a world of sword and sorcery, he finds himself possessing a fragile, powerless body with a strange “System” that seems broken. Initially thinking he's doomed, he learns that by pretending to be weak, he can manipulate others into revealing their secrets, granting him abilities they possess. As he rises in power, he discovers that the System was intentionally sabotaged—by none other than his own future self.

He was very happy to be reborn, but why was he sixteen again, he can’t bear to look back at that time.

Why does he return to being sixteen years old, yet still meet Doomsday?

It’s alright to encounter the end of the world, so why did he have to fall in love with someone?

Even if he falls in love with another person, why did it have to be a man?

Falling in love with a man is also alright, so why did it need to be a secret one-sided love?

Even a secret and unrequited love is alright, so why is that man his….

- Description from Novelupdates