The World's Best Assassin: To Reincarnate in a Different World Aristocrat

Pretty young women have been captured and are being sold off at an illegal auction; by royal order, Lugh the assassin, begins the investigation of Marquess Collide.

The Assassin agrees to kill the Hero because he wants to experience the happiness he didn't have in his previous life; he's reborn as a child of the Tuatha Dé family.

Dia gives Lugh a gemstone that can measure his magic capacity. Lugh's father assigns him his first assassination job.

Using his mana vision, Lugh attempts to find someone who can be both his personal servant and his assistant during assassinations.

Publically a family of renowned doctors, and assassins behind the scenes, the house of Tuatha Dé is the right hand of the kingdom; trusted to become his father's heir, Lugh assists his father with his mission.

A group of girls were toughing it out despite their impoverished circumstances, but an orphanage captures the girls and forces them to move into the facility.