A Record of Ash & Ruin: The Grieving Lands - Book 2: Glossary & Dramatis Personae

A man was transported to Ancient China and eventually became a servant of a declining household without a male heir. He utilized his wits and modern knowledge to help the household and eventually become trapped in the sea of political turmoils of the period.

- Description from Novelupdates

Qiao Yanzhou is a video gaming streamer.

Gu Zixing is a professional gamer.

Qiao Yanzhou is a big fan of Gu Zixing.

Gu Zixing is Qiao Yanzhou’s idol.

Qiao Yanzhou is a quiet fan.

Gu Zixing is a cool and charming man.

Qiao Yanzhou is a couch potato.

Gu Zixing is a world champion.

A ranked game brought the two together, and the chemistry between them takes an unexpected turn…..

Not long after:

Gu Zixing: Xiao-Qiao, am I still your idol?

Qiao Yanzhou: Yeah.

Gu Zixing: Can I kiss you then?

Qiao Yanzhou: Sorry, who did you say you were?

- Description from Novelupdates

In the middle of a deserted island, a small boy wakes up with two sets of memories: one from his few years of life and the other from a man who lived to adulthood and achieved great things. When he least expected it, a powerful master appeared on the island and took him in as a disciple, revealing a shocking fact: magic exists in that world, and, thanks to it, humanity managed to conquer the galaxy.

After experiencing heartbreak from being abandoned, he enlisted in the military.

And then, he became a war hero.