Minato Namikaze was many things. The fourth Hokage. A hero of the third ninja war. The first ninja in history to ever earn a flee-on-sight rating from a major nation. A loving husband, a proud father, a sealmaster, and much more. But right now, more than anything, he was exhausted; it had taken everything he had to match that masked man without allowing Naruto or Kushina to be harmed when they couldn't move, much less defend themselves, and a fair few things he didn't to defeat the most powerful of the Biju without letting Konoha be crushed as collateral damage. Even with all that, it wasn't quite enough. Rather than his own strength suppressing the monster, that task had fallen to Kushina and her adamantine sealing chains, never mind that she was halfway into the grave herself. It wouldn't hold the fox long, of course, but it would have to be enough for him to imprison it in someone else.
"It's too powerful for a child. It was nearly too powerful for me, and I was much older than he is - old enough to know what I was getting into, and to be prepared for it."
"He's our kid, Kushina. I know he can handle it - I already know he can handle anything he puts his mind to, and the new seal is much more secure than yours was. It won't require active upkeep and constant willpower from him to keep the fox controlled like you did, not while he's young - if he decides he wants to loosen the seal when he's older so he can use more of the fox's power, Jiraiya will have the key. I'll leave it with the toads."
"Minato, I love you, you dork. And if I didn't have to give everything I have to hold this furry asshole down right now I would kiss you for it. But trust me on this one - I have more practice restraining the fox than anyone alive, and I'm an adult ninja, and it's still taking everything I have just to keep this bastard pinned. If there's anything wrong with the seal, even just some minor error we overlooked, you're asking a impossible task of a child to not let him loose. We need an active ninja; even if they're not an Uzumaki, it'll still be safer. Damnit, where's auntie Tsunade when you need her?"
"I hardly think what Senju-hime needs is more power to throw around while drunk."
Minato begins to laugh at his own joke, then aborts halfway through, wincing in pain from the burns inflicted by the Biju's caustic chakra during their clash. Then he starts, as though thinking of something brilliant.
"I've got it. I'll have the shinigami rip the fox in half. I'll take the yin half with me to the grave, and we'll put the yang half in Naruto. That way, it'll be somewhat more manageable for him to deal with!"