It was purely chance that they met. They shouldn't have, to be honest, not with their positions as Dragons. It wasn't like it was a bad thing for Dragons to meet, but they were not supposed to leave their villages. But one was just a boy who didn't know how to be still, and the other a man who ventured outside his village borders to protect it, despite the villagers fear for him.
It was during one of his excursions to annihilate pests that were after his powers that he encountered the brat. A brat with shackles around his ankles and chains tangling around his legs.
Most likely, it was because of those chains that he had gotten caught, and it was, perhaps, just a stroke of luck that the kidnappers weren't satisfied, and were out to catch more monsters. Ao didn't even need to use the power of his eyes to defeat the thugs - he was proud of having grown stronger, strong enough so that maybe the previous Seiryuu could be proud of his strength. He killed all except the kid, who was a scrawny little thing, with his long green hair an unruly, dirty tangle and his clothes nothing but rags.
He didn't know why, but for some reason, the kid feels familiar, and evidently, the kid feels something of the sort too, at least judging by his expression.
The kid trudges after him to his cottage, for some reason. He doesn't get why, but he finds that he doesn't particularly mind. For some reason, they share what little food Ao has, and for some reason, the boy curls up beside him. For some reason, Ao can't tell him off.
But he's been lonely for so many years, so perhaps that's the reason.
The too skinny boy sleeps calmly beside him, and for some reason, Ao thinks that that's good, because he looks like he's not had a proper nights sleep for a long time.
It's early morning, still almost dark, when the door to his little house burst open and Ao, who isn't used to peolpe barging in on him because they're so scared of him and his eyes, is blinded by the sudden light of torches.
There's shouting, and the kid clutches to Ao in something that might be desperation, and Ao growls angrily as the boy is ripped from his arms. The teenage Seiryuu bristles, snaps at them angrily, and the people of his village who dared relatively close explained that the strangers who had appeared were the boys guardians, that he had to go back with them.
Ao's eyes flash dangerously, and, despite knowing that there will be severe repercussions, he uses his power against the people from both his and the boy's village.
But he's still young, and lacks the control of his powers. He never had anyone to teach him. Soon, all too soon, he collapses, exhausted, and blacks out.
When he regains conciousness, he's laying in the dirt road, and it's raining.
The boy is nowhere near in sight, nor are the people claiming to be from his village.
He can't go search for him, is not allowed. After all, he can't leave the village, not really, not until the day he dies. Even if he wants to go find him.
Because it feels like a piece of his soul had been ripped away, after finally having been put together again, after centuries of yearning.