That Time an American was Reincarnated into Another World - Chapter 218: Authority 7

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

Xiang Shaoyun is the young master of an influential and powerful sect and is blessed with an extreme latent talent in martial cultivation. From talent comes confidence, and from confidence comes a declaration to give all the so-called geniuses a head start of ten years before catching up to them.

Born into the powerful Moonviel Alpha bloodline, Celestia Elizabeth Moonviel was destined to inherit her family's legacy,until betrayal shattered everything. When her father, the ruthless Alpha of the Moonviel Pack, falls for a noble Vampire, it sparks a forbidden affair that destroys their family and ignites an all-out war between Werewolves and Vampires.Branded as a traitor's daughter, Celestia is forced to flee as her own brother, Lucien Moonviel, plots to eliminate her and claim the family empire for himself. With enemies lurking in the shadows, she finds an unlikely protector in Draven Nightshade, a dangerously charming Billionaire Vampire with his own hidden agenda.But Celestia soon discovers that the war is not just about power-it's about her. The child of her father's affair is prophesied to hold the key to supernatural dominance, and Celestia is the only one who can find him. Torn between vengeance and survival, between the fierce loyalty of her werewolf blood and the irresistible pull of a vampire's touch, Celestia must uncover the truth-before the past destroys her future.

The story is about a boy entering high school, who answers a strange call from a public phone one night. The caller challenges him to a bet: She’ll remove the birthmark which he sees as the cause of so many problems, and he’ll have fifty days to win the heart of a girl he’d considered far beyond his reach. And with this, a very strange summer begins.