Long Qingao wasn't a normal member of the Long clan. Rather he had a very specific identity there.
He was the only external clan member that had managed to fully awaken his guardian bloodline. With that, he had rapidly risen in status in the Long clan.
All this had happened a long time ago, of course, and over a hundred years had passed since that day. While his rise was quick, Long Qingao had ended up getting stuck at his current cultivation base.
It wasn't that he was facing a bottleneck, but rather that his body couldn't handle his bloodline at all. Since he was an external member of the clan, his original bloodline was very thin.
Normally, a person like him should have never been able to awaken it at all. And yet against all odds, he had done it. It was also because of that awakening that he was in this situation.
