One Piece: King of the World - Chapter 3 - : King Engine?

Meet Sora and Shiro, a brother and sister who are loser shut-ins by normal standards. But these siblings don’t play by the rules of the “crappy game” that is average society. In the world of gaming, this genius pair reigns supreme, their invincible avatar so famous that it’s the stuff of urban legend. So when a young boy calling himself God summons the siblings to a fantastic alternate world where war is forbidden and all conflicts–even those involving national borders–are decided by the outcome of games, Sora and Shiro have pretty much hit the jackpot. But they soon learn that in this world, humanity, cornered and outnumbered by other species, survives within the confines of one city. Will Sora and Shiro, two failures at life, turn out to be the saviors of mankind? Let the games begin…

The Priest of a nameless God, Kyle.Forsaken by the ones he once called his companions.

He had crossed into the dark, ruthless Wizard World.Lucien found his system somewhat different from the usual golden finger.System upgrade points? Chip activation?None of these, but rather becoming a role model, transforming into a nurturing breeze:Teaching students knowledge, receiving advanced knowledge in return.Caring for and maintaining students, earning generous rewards.[Your student has mastered the Magic Potion “Kuru's Cough,” congratulations on acquiring the improved formula “Kuru's Cough - Enhanced”!][Your student has mastered witchcraft “Fireball,” congratulations on learning witchcraft “Greater Fireball”!][Your student has successfully crafted the wizard's tool “Pale Mask,” congratulations on acquiring the wizard tool’s manual “Revised Pale Mask”!]Initially, Lucien was resistant.But after experiencing what it was like to teach disciples and outdo them, Lucien felt he had completely transformed into the form of the master system.This thing, isn't it much more useful than something called Cheating Device?

You are the ruler, I am a subject, you want loyalty, I’ll give you loyalty. You are the ruler, I am the subject, you want my sacrifice, I will sacrifice for you. This lifetime, we’ll only be ruler and subject…… cannot become the one who accompanies you to experience everything.

A deposed empress, a failure of a substitute. Charging into battle, he was the emperor, and she, his general. But within the intimacy of their military tent, he was her husband, and she, his wife.

But everything was star-crossed. For the one he loved the most, he would push her into hell again and again.

- Description from Novelupdates