Disclaimer: I don't Own Naruto. I don't own Bleach either.
Summoning the Shinigami
It was the worst night in Konoha's history. The Kyuubi no Kitsune was closing on them, its enormous tails swaying around, destroying everything in their paths, its gigantic paws crushing everything they stepped onto, its sharp teeth biting through everything that was so unlucky to get close to them. The shinobi of Konoha fought valiantly, in an effort to slow it down, but the monster was relentless in its approach towards their home. Their hopes were relying on the Yondaime Hokage, their beloved leader and recognized genius in their world. Surely he would be able to stop the demon, wouldn't he?
"The Yondaime is here!" The shout lifted the spirits of everybody on the battlefield. Their courage was almost broken under the Killing Intent of the beast, but now they found the strength to fight again.
Namikaze Minato wasn't feeling so confident, and it wasn't only due to the price of what he was attempting to do. Sure, he checked his seal design for bugs and was sure there weren't any, but that changed nothing about the fact that it was an untested jutsu. Who knows what could happen? And how would the God of Death respond to the summoning? Only one way to find out. He brought his hands together and ran his fingers through a sequence of seals.
Mi, I, Hitsuji, U, Inu, Ne, Tori, Uma, Mi.
„Shiki Fuujin no Jutsu!"
He felt a disturbance in the air behind him accompanied by a chill, signifying the appearance of the Shinigami. He braved a glance behind. There stood a truly fearsome apparition, taking the form of a huge man in black with hair done up in spikes ended with bells and an eyepatch and a katana at his waist. Minato didn't know what he was expecting, but he somehow felt something was wrong here. But he couldn't back off now.
"Shinigami-sama," he spoke, "Please assist me with defeating the demon in front of us. In exchange…"
"Oh, a battle!" the man in black interrupted him enthusiastically and rushed forward. Minato could only stare open-mouthed.
The battle that followed was unlike anything the Yondaime, or anyone in Konoha, had ever seen. The summoned man charged at the Kyuubi with an old rusty sword. The Nine-tails didn't think much of him at first, but quickly had to change its opinion. It had to, after the jagged blade cut of two of its tails before it could turn around. And unlike the wounds caused by Konoha ninja's jutsu, these wounds didn't close almost as soon as they were inflicted. They didn't heal at all. It didn't take long for the Kyuubi to lay on the ground in a whimpering mass. The Shinigami, or whatever it was, didn't relent in its attack. A couple of sword strokes later and the once so fearsome demon dispersed in a mass of chakra.
"Ah, now that was what I call a good fight," the summon, his clothes completely torn, stated. "Too bad I have to go now. Bye!" and he disappeared.
Minato stood on top of Gamabunta's head, surveying the damage. Half of the forests around Konoha was leveled, there were valleys and hills where there were none yesterday, part of the wall surrounding the village was broken, but thankfully only training grounds were close to it and no significant damage befell the residential area. It was a far cry from the outcome he imagined, but he was still alive and nothing happened to his son, so he wasn't complaining.
"Minato, what the hell was that?" The Boss Toad asked slowly.
"I don't know," the Hokage answered, "and I don't even want to. But this technique should better be forgotten."
"I can't agree more," Gamabunta nodded before dispelling.
Minato landed gracefully on his feet. The shinobi of Konoha were gathering around, cheering on him. He shook his head. He had a village to govern, he would have too much on his mind to think about what he had just witnessed. Oh, and he had to come up with an explanation to this. He sure wasn't looking forward to that.
So this one-shot is over. I started writing another with a different Shinigami, but got around one sentence into it. I might finish it if you are interested enough (and if I'm inspired enough).