You can continue slice of life. My opinion is instead of the MC going to other worlds, make the girls come to his world. iIthink it's much better. It's just an idea
But he is not a normal person. He is a reincarnator who had watched Naruto and even read more than hundreds of fanfics. So as any fanfic protagonist, he dreamed big and thought he could simply master 8 gates and FTG and become godlike powerful after getting Rinnegan.
Naruto: My Top Tier Lists can grant people power, but not to Myself!