World Development System - Chapter 312: 243. The Blood-Bone Marrow cleansing pill

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…

Grandpa Yu often repeated beside the ear of Yu Zhen, saying that he(YZ) has a soul in his body. If he doesn’t properly train in asceticism, and raise then send away the powerful soul, in this lifetime he would have to live as a bachelor. In his next lifetime he would be reborn as a lifestock animal.

Yu Zhen played on his mobile and nodded. On the surface he replied, “Uh-huh”. In his heart he laughed, “hahaha”. Keeping his grandfather in the dark was amusing so the lie was repeated for over ten years without Yu Zhen getting tired of it.

After some years, Grandpa Yu passed away and a cold-faced handsome guy came to his door in a luxury car – with a household register in his hands.

…..

Yu Zhen: The soul in my body reincarnated into someone else’s body to demand repayment, what should I do!

- Description from Novelupdates

Upon meeting the girl who would become her adopted younger sister, the duke’s daughter Christina regained memories of her previous life. Through those memories, she learned that her new sister, Mishuli, was the heroine of a certain story. And though the story depicted a Christina who abused her sister, the real Christina turned into a siscon who spoiled Mishuli to no end.