MTL - The Devious First-Daughter - Chapter 632 Planning, the mind of Qiongfeng Gongxia

Sano Yuji, a black company employee, is summoned to another world while finishing his work at home. His profession in the other world, a Monster Tamer, is considered a job that makes it difficult to become an adventurer. However, thanks to some slimes he met, which read several magical books, he gained magical powers and the second profession, Sage. Yuji acquired overwhelming power, but is he conscious of his strength? Blindly becoming unparalleled and strongest in the world!

“I'll take this child.” Sold to the Wudang Sect's outer martial arts training hall for three silver coins at a young age, Kwak Yeon dreams of mastering supreme martial arts. But can he overcome the needle-sized gateway barely permitted to trainee instructors and rise to become a disciple of the main sect? “A true gentleman cannot stand idle in the face of injustice!” Thus begins Kwak Yeon's unyielding journey through the martial world, following the ruthless principle of “Kill Buddha, Kill Ancestors”—destroying all obstacles in his path!

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

One day I got a younger sister.Only I know her true identity.