Soon after Naruto reveals his new and improved Super-Harem Jutsu, Hinata returns home, distressed.
Hiashi, hearing sounds from Hinata's room, approaches the room and activates his Byakugan. He sees his daughter curled up in front of a hidden altar of ... Naruto Uzumaki. Reading her lips, she seems to be mumbling.
"Must not think of the possibilities, ... must not think of what a young man of Naruto's stamina could ... So that's what Lee meant by power of youth ... - Epp!" She donned a shade of red that seemed unhealthy as she reorganized her thoughts.
Pausing for a few seconds, she continued "So ... if Naruto and I do that, that would fan our Flames of Youth, right?
And Gai-sensei said you should always help your Flames grow!" He watched as she approached shades resembling a tomato, and clumsily reapplied the complex seals that hide the altar and donned her baggy jacket.
Hiashi moved to her door, hoping to make head or tails of the situation. As he pondered the situation, the door swung open and stuck him on the head in his momentary confusion. Hinata quickly apologized, and bolted in the the direction of the Uzumaki's apartment, yelling over her shoulder something about the Power of Youth as she suddenly appeared on a sandy beach in front of a setting sun.
The next time he saw her, she had moved into the Uzumaki's apartment, in order to ensure her Flames of Youth never dimmed.
He never understood how the Power of Youth gave her such a bad limp though.