I am the only Cultivator in a Mana Dominated World

Ren wakes up inside a novel that he was reading before his death. Ren possessed a character that was never once mentioned in the original novel. How would Ren fare in a world full of dangers and threats. And a protagonist that was busy making a harem instead of saving the world in the story. Suddenly Ren awakens a mysterious system which lets him cultivate in a world of magic. He vows to become the strongest in the world but somehow ended up stealing the protagonist harem, his mom and childhood friend. — Description from novelcodex.org