The change will start to happen as soon as you master your first jutsu. No, I'm not talking about puberty- this is our clan's greatest gift and curse: the Giant trait. I once grew four inches overnight; I was so sore I couldn't move the next day.
Our clan was imprinted with a restless yang(that is to say, physical energy) that our bodies respond strongly to. They feed off of each other in quite a complimentary manner, and sustain each other. They need to. You see, large beasts such as the old dragons could not function properly without the use of chakra, for otherwise they would be too sluggish and lethargic.
That is why if you begin to train, you must never stop. Ask about your Uncle Jun to find out why. But if you do keep training, oh my! You will be so strong. You will have a strength only the old dragons did, and be so big and lovely.
I am sorry I will not be around to guide you as you grow. I am old, and when our kin reach my age, our health goes quickly. You will probably be hunted. The high and mighty ninja of this age see our clan as a relic of a bygone era, and will fear you as they did the dragons. But they forget how much good the old dragons and our clan did: mountain strongholds no army could break, making rivers and lakes where there were none before, giving hardened adults a child-like joy they had forgotten. Be strong, little Akemi. My heart will always be with you.
~oOo~
So Son Osu traveled to the narrow pass, for that was the way to the dragon that kept watch over the river with the healing water. Upon arriving at the pass, he found his way to be blocked by a giant, a man with a fearsome gaze and wild hair!
"Giant! Move from the road and let me pass," Son Osu said.
"Wahaha! This pass is mine, and mine it is. You shall not pass as I do live!" Spoke the giant with a mighty laugh.
"I seek the wise dragon," Spoke Son Osu. "That I may speak with him, and carry his waters to my village elder."
"Though the dragon past me lies, I shall not let you pass by!" Spoke the giant.
"Giant! If I can perform as you in a test of strength, will you let me pass?" Son Osu asked.
"If you best me, that is fine, for no strength surpasses mine!" And so the giant took hold of a large and weighty boulder, taller than Son Osu, and lifted it high over his head. With a mighty laugh he let it crash! to the earth in front of Son Osu. Son Osu looked within himself to calm his breath, and used the wisdom taught by his village elder to mould his chakra into the essence of the wind, lifting the boulder on the winds even higher than the giant did!
The giant was stricken with shock, and spoke, "I have just been bested! Fie! I will move, now pass you by." And it was in that manner that Son Osu bested the giant, and at last came to the river of the dragon, and there the boulder remains to this day.