Minato take decision to use his Dead Demon Seal, to save the cillage and the country Minato sacrificing his life. Kushina refused her husband plan but after Minato give her explanation about why he has to do this, Kushina understand it and accept it. Minato used the Dead Demon Seal and sealed a half the nine tails's chakra and used The Eight Trigram Seal to seal it inside Naruto. But before the sealing process completed, the nine tails attack them. With their life, Minato and Kushina protected their son until the death. Then Minato summoned Gamatora and entrusting the key to the seal. Before Minato do the last step to finished the seal, he ask his wife for probably she has anything left to say to Naruto. Yes, Kushina has a long word to say but she only has short time.