A Figure of The Past (Naruto) (DISCONTINUED)

-A Figure Of The Past (Naruto)-

Short Summary-:
An unknown young child shows up in the Hokage's office, asleep. Unfortunately, the Third Hokage is currently outside doing whatever, so the ninjas there end up attacking and attempting to capture the person before the stranger single-handedly defeated all the ninjas available. While most were knocked out or too exhausted of chakra to move, they just quietly waited for someone, presumably the Hokage since the current location was... well... the HOKAGE'S office. Finally the Leader of the Hidden Leaf arrives, and as soon as he sees the figure, he runs up to them, encasing them in a strong embrace before they poofed, disappearing. The once-crying-in-happiness old man was now staring at his hands, dazed, confused and shaking before a small sigh was heard from behind him. He turned around before again grinning. "You're finally back!"

-x-
Who is this person? Is it a girl or boy? How old are they? Who are they and why does the Hokage know them, mentioning: 'You're finally back!'...?