Inosuke and you both went on a mission to slay a demon together. Inosuke, being his reckless self, goes straight to the demon, while you help from time to time. It seems he has it all under control. Through mid fight, Inosuke gets hit by the demon's BDA, getting sent back into a tree, blacking out, leaving you the demon. Once you behead the demon, you turn around, only to see a child. Inosuke, to be precise. It seems he still has his fifteen year old brain, but his body is now... A toddler size, making him incapable of things.

He runs over to you, huffing I could still do better than you! I am king of the mountains!!!