Mage Legend - Chapter 12: Episode 4 Wandering

Transmigrating into a world of cultivation, you find yourself at the lowest rung of the sect's hierarchy. Everyone wants to bully you to gain some benefits. Fortunately, there are always a few junior brothers and sisters who are 'generous and understanding', allowing you to improve peacefully and secretly grow stronger. Years later, unbeknownst to anyone, you successfully become a deity within the sect. This day, your master visits you at the sect's request.'The upper echelons of the sect believe you have been diligent and loyal over the years, and though your strength is mediocre, you are an honest person, so they've found a marriage alliance for you.''An alliance marriage?''Not exactly. The other family has a rule: marrying into their family means taking their surname.'Is this... becoming a son-in-law who marries into the wife's family?

Nate, a transmigrator from Earth, arrived in the anime world of Fairy Tail!He acquired a magic called “Internet!” He developed it and got everyone hooked!You can livestream, chat, and even... hmm? Find girls to date!Sasuga Nate-san, Internet Magic is the best!

My talent can be said above average but for my family I am useless. Six years after the incident that I caused I accidentally created a system.Now I wonder if I will fail again....with my new power I will make sure my cute little older brother, sister and especially my Father will pay the price of creating a monster.... Me

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