Author's Note: Um, I don't know. Neji has a way of making you introspective and angsty. The Hyuuga clan just annoys me, to be honest; something about all of those children screams 'incest'...
The Byakugan is more about knowing than seeing; the Hyuuga compounds are full of hot air, their histories filled with swaggering contests and reasonless oppression. Their eyes aren't about seeing the truth, only what they want to and for the purposes they so select. But they're his and they're divine, and you call them to life like this:
First, you have to conjure the hate. It's born in you like a latent gene through incest and growing up in their big, quiet house: albino orbs and a shroud evolved as you live among people who are constantly judging and picking out the weakest. Natural selection, they say- the smart live, and you've got to play by the Hyuuga's rules in order to survive, let alone activate your birthright. It's that anger inside, hidden behind shojou screens and brought to life by unscreened insult; it's a desperate contest that brings your Byakugan out, so you can learn to see who or what's waiting around the corner, ready to dominate you.
Once you've got that, it's a cinch: make the seal (oddly, it's an upheld middle finger) and let it all fall into place. Remember dead daddies and the disapproval in your elder's eyes, remember how you're constantly fighting in the drowning pools to keep from being torn asunder by the other, kicking bodies who's DNA you happen to share. Think about everything (everybody) that stands in your way because you're a Hyuuga, and let your limbs slide until you're at ease on steel tightropes.
And there: with these eyes you can see the fullness of human character, with all it's potential for contempt. Now go and fight, and see if you don't come out with an attitude like Neji's.