Question

Who is the Fourthage who sealed the Nine-Tails inside Naruto?

Answer 1

I believe there might be a typo in your question. It should be "Who is the Fourth Hokage who sealed the Nine-Tails inside Naruto?" The Fourth Hokage who sealed the Nine-Tails inside Naruto is Minato Namikaze, also known as the Yellow Flash.

Answer 2

The Fourth Hokage who sealed the Nine-Tails inside Naruto is Minato Namikaze.

Answer 3

Minato