The Desolate Era (Web Novel) - Book 1, Chapter 8 - The Moon in One Hand, the Sun in the Other

A good-for-nothing man married a beautiful girl but was kicked off the bed on the wedding night. Furiously, he wrote a bill of divorce and ran away.
He was schemed a car accident in which he nearly lost his life. However, it turned out to be a blessing. He swallowed the soul that passed through the outer world, thus obtained superb medical skills and martial arts.
Later on, with the silver needles and invincible martial arts, he embarked on the road of counterattacks and was committed to his great dreams.

- Description from Novelupdates

My girlfriend is too beautiful.

And, she treats me so nicely.

I didn’t even confess, I was confessed to.

So…

Why me…?

Leon and his father, Artorias, are the last remaining scions of a once powerful and illustrious family of lightning mages. After barely surviving an attack that destroyed their home fifteen years ago, they now live in the dangerous Northern Vales, a desolate wilderness far away from civilization. But those who want them dead are strong, patient, and relentless, and it is only a matter of time before they find the two they seek...

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.