They were all in a hidden cave, Kushina was crying out in pain. Minato was keeping the seal together and Biwako, Hiruzen's wife, was assisting in the birthing process.

"Is this normal?" Minato asked, worried about his wife's well being.

Biwako grumbles about ignorant men and says "A man couldn't handle the pain so that's why women give birth" to the sweatdropping Yondaime. The sound of a crying baby echos in the cave as the first born, Naruto enters the world. All seemed to be going well as Menma and soon following Mito were born withen the 10 minutes, until the masked man appeared. He had apeared out of thin air as he already killed the guarding anbu and Biwako.

"Step away from the jinchūriki," Mandara, the masked man says holding Naruto hostage.

"Ok now let's calm down," Minato says in an almost pleading voice.

The masked man raises his eyebrow, not that they could see, and replies "Speak for yourself Yondaime, I am perfectly calm," then he throws Naruto in the air, kunai ready for the baby to land on.

"No!" Kushina cries out before Minato hiraishins to Naruto, tossing the blanket off with the exploding tags attached. Minato grabs his children and teleports them to a safe ware house near the sand border. He teleports back to see that even he, the yellow flash, wasn't fast enough as the masked man had already set the Kyūbi free and was controlling it to attack Konoha. The mask man disapears and reappears in the forrest facing Minato. They attack eachother at kage level speeds as the masked man throws a kunai at Minato cutting a single hair, and Minato using a wind jutsu nicking his mask.

"Who are you," Minato demands.

"I am Mandara Uchia!" The masked man shouts laughing maniacally,(it is actually Mandara). Before he could disappear, Minato hits him in the back with his rasengan paralyizing him. The masked man goes to the warehouse and before he died drew a star within a circle with kanji with his blood and curses Naruto before Minato finds him and stabs him in the heart finishing the job. Minato already new what he had to do as he always planned for the worst sighed and grabbed Naruto, Menma and Mito, not even noticing the curse that Mandara had put on his eldest child. Minato summoned the demon sealing altar placing his children on it. He planned to use the reaper death seal and seal the yin into Menma, yang into Mito, and the soul into Naruto. Kushina had recovered quickly and realized what Minato was going to do.

"No! You can't place that burden on our children!" Kushina shouts.

"It is the only way," Minato smiles sadly, knowing that this will be the last time he will see his family. He summons Gamabunta, already preparing the handseals when Hiruzen knocks him out.

"I am sorry successor, but I have lived a full life and I want to join my wife" Hiruzen says. He performs the necessary hand signs but his plan was different, not only splitting the chakra, but the soul too into Menma and Mito. He knew the soul was needed to control the chakra, but didn't know Naruto was on the altar. The first part went well sealing the the fox into Menma and Mito, but then the Shinigami's eyes widen as he is sealed into Naruto, with the Faustian seal, the seal Mandara drew on Naruto. The Faustian seal (if you watched Black Butler you should knowthe basics). Is a slave seal made by a demon between a true demon, like the Shinigami not Kyūbi as he is part of the jūbi, and a human mortal that dictates that the demon is essentially a slave and has to complete their human master's goal. In return the demon gets to consume his soul. It is different in this case though as Mandara wrote the seal and it was on his back. So the Shinigami wasn't able to serve Naruto directly, and in return if Naruto fed the Shinigami 1,000 souls his own soul wouldn't be consumed once his goal was achieved.

Later that night Minato gave a speech. "People of Konoha, the Kyūbi was defeated by the Sandaime and sealed into my children Menma and Mito, they are the saviors of Konoha." Minato figured out that the soul wasn't in Naruto as sensed no malice or anger inside Naruto. But what he forgot was a crying Naruto in his crib alone with grey cloth wrapping around him turning his hair grey, skin deathly pale, and eyes a hollow stormy grey blue. A dark skeletal mask briefly appeared on Naruto's face, signifying the Shinigami's service to him.