MTL - One Punch Man: Eight Strange Skills at the Beginning - Chapter 30

After an unexpected death, a soul finds itself reincarnated into the body of Itsuka Shido, an ordinary teenager in a world filled with powerful spirits, magic, and dangers from other dimensions. With the help of a mysterious system integrated into his body, Shido gains the ability to travel across worlds, summon legendary anime characters, and unlock a wide array of random skills and abilities.Disclaimer: The cover isn't mine, credits to the original artist.

While returning home from a boring day of work, a black hole opened up in front of John and sucked him in. Before he was floating in the blackhole, a helmet latched on to him. "Uploading A.I under progress...Activating Survival Kit" A weird robotic sound appeared within the conscious of John and suddenly a white energy enveloped him... After opening his eyes, John noticed he was teleported to a whole new world. A world of magic and he was a user of a system. Arkon, the world John was brought too, was a medieval world which is 10 times bigger than earth. This new world held many new mysteries and this was the beginning of John's adventure. John will dominate and stir the world with his new system. Old technologies begone and use my advanced techys instead! Ha! you want to hold a politic, economical and military war with me? Sorry but my system is too broken for you all to counter.

The MC entered the body of the An family eldest son, An Ziran, an arrogant 16 years old boy who weighed 78 kg (~171-172 lbs), who only knew how to eat, play and sleep. Seeing his current body, An Ziran decided his first priority was to LOSE WEIGHT!

Three days later after he became An Ziran, An Ziran’s father and his biological mother died, which meant as the eldest son he had to take over the family business.

Beside his legitimate first wife, An Ziran’s father also married 3 others women, who all wanted to take over the An family fortune but only the eldest son could be able to touch it, therefore they have to depend on An Ziran in order to live a comfortable live.

An Ziran’s father also had an older brother who is always planning to steal the An family fortune. The elder brother of An Ziran’s father and the woman he married had powerful connections. In order to save the An family fortune, An Ziran has to find a golden thigh to cling on. The butler told An Ziran that there is an engagement between the An family and an influential family. Therefore he takes his sister to that family house to make a connection.

However, during their journey, An Ziran’s younger sister overheard that the son of that family is UGLY, so as a beautiful and spoiled young lady coming from a rich household, she didn’t want to marry him and decided to run away. Without any other choice, An Ziran had to take his sister’s​ place and marry that man, who told him that he would let him go soon, but lied.

- Description from Novelupdates

The dominant forensic doctor who traveled back in time to the era of the Great Tang's Zhenguan reign, became a distinguished family's abandoned girl.