Invincible in other world

Den is a 20 year old normal guy who is going to complete his college graduation. His life can be called pretty normal. It was neither too tough or too hard and maybe this was the reason he has been always bored of it. One day when returning to home. One day he got transported to another world and first thing he confronted was a monster much stronger than him. When Den thought that it was the end of his life things turned differently as monster couldn't kill him no matter how hard he tried. This is the story of our invincible protagonist in a different world . Warning : It contains mature content.