Death March kara Hajimaru Isekai Kyusoukyoku (WN) - Book 15 - 15-23. The Forbidden Science

Stumbling upon a game, I found myself immersed in a script brimming with excitement: superpowers, oddities, curious artifacts, and demons...Here, one can not only delight in the pleasure of grinding but also touch an infinite degree of freedom and even experience the curious thrill of being carried away by monsters!Let’s not talk too much, happiness, just happiness is all that matters!

There is only one Magi Craft Meister in the world. After the death of the last Meister over one thousand years ago, Jin Nidou was transported to another world in order to succeed her will.

21st century kid got onto a virtual game 600 years into the future, with a freak combination of events gets to play as a NPC!

The first system job is to undertake the roles of helping new players create their character. Want to choose as one of the hidden race? OK, this is a slavery contract, up to you to sign it or not!

Entering the game as a player and creating a personal game character, the only advantage I have… The choice of selecting a powerful race!

Walking alone to the peak, bringing the present world to advance by leaps and bounds, the abnormal path starts from this first step!

- Description from Novelupdates

Zhangsun Zijun and Yi Xichen are the protagonists of the novel “Record of Nine Thousand Vicissitudes.” One is solid and reserved; the other is free-spirited and uninhibited. As fellow disciples under the same master who grew up together, the two have a deep friendship that was strengthened by their numerous life and death adventures together.

However, in a popular yaoi fanfiction, the personalities of these two characters is completely OOC. Zhangsun Zijun turned into an insanely jealous, insatiable s*x addict madly in love with his wife Yi Xichen. Yi Xichen turned into a sweet, delicate little angel. Their daily life was full of kinky bedroom activities…

Suddenly, the Zhangsun Zijun character from the fanfiction was transported into the world of the original novel.

- Description from Novelupdates