Generally speaking, it is a story about traveling from modern times to the ninja world, and then finding a way to go back.
Modern character design:
In the late stage of the control, Hashirama is eager to marry his younger brother and become the next Prime Minister of the Senju Consortium, Tobirama is a scientific research fanatic, Madara is the administrative executive of the Uchiha Consortium, and Izuna is the real manager of the consortium and is responsible for gray affairs.
Approximate world process:
Modern → Creation → Four Ninja World Wars → Modern → Breaking through the world wall to achieve interpenetration
cp: all Tobirama (Hashirama and Madara and Izuna → Tobirama)
Time Travel Quoting Honkai Impact Three World Views
Intent: On the degree of difference between similar and dissimilar world bubbles