MTL - Pampered Fei Brimming with Cuteness - Chapter 2009 : Extra 121

He Lang died by his own hands for the sake of his imperial younger brother’s ambition, whom he loved. He was offered to be reborn in exchange for giving up his past romantic feelings. Reborn without the burden of his romantic feelings, he brings with him a manual to new worlds. He wholeheartedly followed the instructions of the manual to complete the tasks, not knowing that the originally slag gong was blackening…
He pleaded to his affectionate Emperor brother to release him, he pleaded to the paranoid prisoner next door, but until the end he remained baffled.
In the end, he discovered that the full name of the manual was – “Slag Shou Cultivating Manual”
Σ (っ ° ° °;) っ!

- Description from Novelupdates

In the middle of the night, looking at the woman in his embrace, he smiled devilishly, “With your discontentment, do you want me to continue?”

Shiro Sakamaki was reborn into a new world with one simple goal: to live a peaceful, luxurious life free from drama.But when he transfers to a prestigious high school in Tokyo, he quickly discovers that his new reality is anything but ordinary. The city is a strange mix of supernatural forces, ghostly phenomena, and events that feel like they’ve jumped straight out of an anime.Before long, bizarre occurrences follow him everywhere, along with a series of beautiful, mysterious girls—from the arrogant, blonde twin-tailed exorcist, to the mysterious quintuplet sisters, to a passerby heroine with hidden powers.As Shiro gets tangled in the supernatural chaos, he realizes he’s at the center of something far darker. Cursed relics begin to surface, and Ancient, Evil Outer Gods—whose very presence bends reality—start to stir.Now, Shiro must figure out why he’s caught in this web of strange occurrences while trying to survive school and the surreal new world he’s been thrust into.

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.