That's it? That's the big origin story? Man, what a freakin' letdown. Minato is hardly the genius he was heralded as, and the Kyuubi seemed rather pathetic, as well. I mean, it seems like it killed all of three people, those three being Iruka's parents, and Kurenai's father.
Even worse to me, Minato could have lived, but chose to die. Sealing the Kyuubi in Naruto wasn't his only option. I really don't like that man.
He manged to destroy Madara's arm, upto this point no one else has managed to harm him, not even when Itach planted the Ameretsu in Sasuke's eye did as much damage, The bloke just became a father, his wife is dying, and the villagers he's sworn to protect are being attacked by the beast that was sealed inside his wife just moments ago. The fact with all that on his head he managed to divert one of Kyuubi's attacks, attack Madara and teleport the Kyuubi along with his blast away from the village shows how powerful he was.
He also figured out who the Masked man was and the potential threat he would be in the future, this all proves he is a true genius.
Minato could not have lived, he knew from Jiaraya's warnings and seeing this man he had to seal the Kyuubi in his son to give him the power needed to win the war which without the power the world woud pretty much be destroyed.
But Kushina was planning to kill it by sealing it inside her.... that would've made Madara say bye-bye to his plans.
No Kushina sealing it in her and dying would have been a temperory fix, Kushina said he'd be dealt with for a while, but he'd come back later on, somehow. Minato did what he did because he knew that power would be needed and he trusted his son would be a vital key to the lives of thousands of people, also would mess up the balance somehow so who knows what disaster messing with the balance would do.
What I'm surprised about is half of the Kyuubi's power is sealed away yet it still kicks the other beasts butts, how powerful was the Kyuubi full strength?