Eleventh World (Slow Burn Soft Harem, Light LitRpg)

Sol Sauvage was isekai'd through ten worlds, ten years each.

Each world had its own set of rules and magic and he was never allowed to use borrowed power from one to the next.

He mastered a class on each world to survive, Monk, Assassin, Paladin, Summoner, etc...  He also found a romantic partner on each world.

At the end of his journey on the tenth world he didn't know where he would go next.

He returned to Earth at the exact moment he was taken, 22 years old, on a coffee run for his cheerleader friend.  

He quickly realizes all of his cumulative classes and stats are active on Earth, but he doesn't yet know what for.

He will learn that Earth is the Eleventh World and that the Ten Worlds preceding his return was just preparation for what would come.

Sol has one year to build an empire on Earth to prepare humanity for the 51 gates opening all around the world.