I Traveled from the 21St World to the 1950S

This book was the inspiration that came to my mind when I was watching Naruto Think about a time in the 1950s. If Naruto had Obito's ability, it would be no more powerful than space or system space. And I changed the space a bit. I changed Obito's space into another kind of space. What kind of space did I change into? The kind of space with a small world. And I think it's too boring to have only the protagonist alone, and also add a fat man who has traveled from the 21st world to him.