MTL - Little Mermaid Dressed As a Scientist - Chapter 102

Li Ke Lin (also Li Colin), a Chinese office worker, woke up to find himself suddenly no longer Li Ke Lin but instead Colin Lee, son of multi-billionaire in America. Having taken over the body of Colin Lee and carefully imitated his manners and bearings, his next goal is to inherit his father’s wealth. However, when his father lists the condition of marrying a woman who feels repulsed by Colin Lee’s (not Li Colin’s) dalliances, and whose very nature is the complete opposite of Colin Lee (not Li Colin), what must he do to gain her affection?!

“A cheat system? Do you take me for a fool? Nowadays, where can you find such a good thing falling into your lap? Scram from my head. Is this is new kind of fraud? Or is this a murderer training system of aliens that contains the ability of hypnotism?”

“No, I am the chaos that whispers from nothingness, the nightmare of all living beings in the Southern Ten Stars, the successor of the unparalleled God and… your elder sister.”

“…I only have a younger sister, I don’t have an elder sister!”

“No, you have one. I am an illegitimate daughter. It’s just that your dad didn’t inform you.”

- Description from Novelupdates

Mu Xiaoke was a fool in his previous life, he and his older brother love Fu Jiayun. He is a little mute who’s a total failure, how could the other person choose him? He shouldn’t have competed with his older brother, or married Rong Yanzhe as a substitute for his older brother, otherwise he wouldn’t have died alone in the wilderness with his corpse never to be found.

God gave him a chance to be reborn. When he returned to his first year in senior high school, he knew that he could not repeat the same mistakes again. He had to stay away from his older brother, Fu Jiayun, and Rong Yanzhe. The person who treated him as a stand-in for his older brother and kept abusing him. This time, he didn’t ask for anything, as long as he could live well.

It just didn’t occur to him that when he kept a respectful distance from those people, they instead came to pester him endlessly. He was in panic and unexpectedly provoked another man who shouldn’t be approached…

- Description from Novelupdates

There are a total of seven sins, and a revelation is made to a young man named Alex that he is destined to become a demon lord, more especially a demon lord of sin called LUST.

It's not like he can change that and because he always knew something about himself was different—not in a physical sense, well, maybe a little—and not in a mental sense—but rather because he is thrown into a demonic war that compels him to accept his new reality.

He was only aware of a difference in himself. Relating to him and the ladies who are drawn to him... Well, it was more or less like he was a magnet in front of all the girls, and all the girls were drawn to him like a metal.