Zenko; Feral

On October 10th, Namikaze Minato made a mistake. The Shinigami, like all deities, disliked being told what to do. Naturally, he punished the man and his son. Now, Uzumaki Naruto grew up isolated underneath the Hokage Tower due to his appearance...until one day, he escaped...

In this version of Zenko, Naruto is not quite sane and wasn't fully aware of being human.

Prompted by the original idea of Naruto oneshot by Kishimoto where he is really the son of the Kyuubi that attacked the village. Instead of Kurama being his father, Minato was cursed into replacing the Kyuubi and sealed inside his own son who was also cursed into becoming the Kyuubi.