The title says it all.
The main character was and some of his classmates got transmigrated from earth into a fantasy world to save the world.
You get it all right. And somehow, he got the body of a demi-human, half human, half reptile. To top it all off, his job was an alchemist. He forgot shortly his real name, so he named himself Syzoth.
He worked with his classmates for a while but then got kicked out.
Why? Because the guy that got the job hero wanted all the girls for himself, and Syzoth was the only other male in the party.
Syzoth did just that, with the humorous knowledge that Syzoth no longer had to make free healing and magic potions for the ungrateful bastards to use.

And so, he lived for a few months. The demon lord lived on, and one fateful day, Syzoth found a beautiful woman sleeping in the woods. Did he know that she was the eldest and most favorite daughter of the demon lord? No.
But even after finding that out, they somehow got married.

Ohh, how he just loved to look at the face of the hero now.