I Have Medicine - Chapter 420: Dealing With the Zhao Family, Part III

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…

Some say reincarnation is a blessing, but for me, it's a dreadful curse. Cursed with endless reincarnation, I've been reborn as a villain 137 times. And all 137 times, I've been toyed with and killed by heroes who are far more cruel than the said villains... If I can't win no matter what I do, then I'll crush those so-called heroes at their very roots. - Quality Fan Translations, Made by Fans for the Fans - Villain Takes Over The Academy

Akira Kisaragi traverses into the Bleach world, unlocking a check-in system.He initially thought that by checking in daily, he could become stronger, soon become the Captain-Commander, join Division Zero, punch Yhwach, kick the Soul King, and marry Unohana...However, the system's style wasn't quite what he had imagined.〈 Check-in complete, obtained Genryūsai Yamamoto's secret roasted sweet potato! 〉〈 Check-in complete, obtained exclusive attribute: King of Normal Attacks, effect... 〉〈 Check-in complete, obtained Retsu Unohana's... 〉Akira's eyes suddenly lit up!“Seems like this might not be so bad after all!”

There is no master god, no system, no exchange, and some are just source codes that are fused in the mind to open up the world, not to be forced or suppressed, but to constantly go through in order to become powerful Look at my infinitely powerful source code …

- Description from uukanshu