Quote Originally Posted by Buffalobiian View Post
He's talking about that case where some cloud ninja was doing something (trying to rape Hinata, from my possibly twisted memory) and was killed while he tried. The Cloud then demanded the body of the guy (Hinata's dad I think). Neji's dad volunteered to go since he was from the branch family. The branch families had the seal on them which would make the Byakugan disappear when they died, along with the seal.

That's the backstory he's talking about.

@Azonalthious: That's the only case we've heard of. At the same time, they told us that the eye was effectively gone so the Cloud can no longer use it or learn from it. We saw a few eps ago that Hyugas go on missions too. A couple could have well died on missions or in wars. It could even have been a spoil of war passed down through his family or something - not entirely out of the question.
Ao does say that his byakugan eye was a "precious" spoil of war, from a battle with the Hyuga clan. Which means that they most probably scavenged it from one of the dead bodies of the Hyuga they fought in that battle. A Hyuga who most likely was not part of the branch family and therefore did not have the seal. A rare chance to obtain that in battle (mostly likely unexpected), therefore precious as he said. And Ao had it implanted in him. He also mentioned that it helped to lift the jutsu that had been placed on the 4th Mizukage.