Ihoujin, Dungeon ni Moguru - Chapter 056: The Neighborhood Demon King X

Xiao Yu, who was a student from modern Earth, accidentally transports to another world and becomes the lord of a territory. Facing an unfavorable situation, he vows to take back his family business, build his new territory, kill all of those who covet his wealth, and dominate the world!

- Description from Novelupdates

Cho Ryu Hyang was good at math from a young age. When he enrolled into the The Theoretical Maths and Martial Arts School, the teacher, Jo Gi Chun, recognized Cho Ryu Hyang’s talent immediately and took him in.

Reborn into an ancient world of hardship, Chen Qing became a scholar who toiled through ten years of cold study, finally achieving fame on the golden list. Just when he thought he'd join the ranks of the literati, marry a beauty, and reach the pinnacle of life, he suddenly found himself entangled in a bizarre and fantastical incident.It was also at that time that he discovered this world was far from simple—there were man-eating demons, heart-bewitching devils, and even the legendary immortals who could live forever but were exceptionally strange!What he found even more inconceivable was... these deadly things seemed... to all have been designed by himself!!!

Seven years ago, she freely and easily abandoned ￥100 and ran away, carrying her unborn son with her. Seven years later, she returned with the lady killer’s genius son, never expecting that her darling son would sell her out to MBS International. Unexpectedly, her immediate superior was the Mr. ￥100 from seven years ago!