One Piece : Brotherhood - Chapter 48

A skilled but unfortunate modern-day assassin was killed in a freak accident. However, he soon found himself summoned to another world by an evil wizard, who had him possess the body of a boy as an experiment. After successfully planning the evil wizard’s downfall, he used the wizard’s body as a springboard to gain influence and power in his new world.

- Description from Novelupdates

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

“I want to be a true demon.”

A boy not older than 20 years wished as he looked at the sky.

After suffering from the trauma for many years, he finally gave up on life.

People called him ugly, demon, and hideous.

He bared with it, but today he finally broke.

With a piercing pain in his chest, he died.

When opened his eyes, Logan found himself in another world and inside the body of a demon.

His wish was granted, but at what cost?

He had no power and was the lowest among the demons.

No one to help, no one to be with him.

But it did not affect Logan. Because he had something else with him.

‘Sin and Virtue System.’

Guiding him towards his goal to become a true Demon.

Logan’s conquest has begun, so be a part of it.

Otherwise, you will miss him.

The true Demon!

However, is the MC the 'only' one to have a system?

Hm?

Read the fucking novel and find out!

After getting hit by a truck, Hayate Kurogami experienced something bizarre. He arrived in alternative world and awakened as Kaiju Maker.Unfortunately, he was forced to leave this world.Sacrificing himself for goods, Hayate reincarnated to another world.A cultivation world filled dangers and charming beauties.Watch our protagonist become stronger, adventuring the vast universes to achieve the highest realm.1st World: Against the Gods