What is a fanlisting?
"A fanlisting is a web clique that lists fans of a particular subject. Unlike most web cliques, a person does not need a web site in order to join. Fans from around the world submit their information to their approved fanlisting and they are then listed to show their love for the subject."- TAFL

Byakuya is Naraku's latest incarnation. He introduces himself as "Mugen no Byakuya" (Byakuya the Illusionist) in chapter 397 but first appears in chapter 396. He's spying on InuYasha with one eye. He's the one that alerts Dokumizuchi to where InuYasha is so he can get him to use the Dragon Scale Tessaiga.Byakuya knows that InuYasha using the Dragon Scale won't just hurt his opponent but him too.

He carries a sword. He can also send his eye out to spy on enemies. After Kanna dies in chapter 480, Byakuya is the only remaining incarnation of Naraku's. Because of the way she died Byakuya knows he needs to be protective of his own life when it comes to Naraku. He's also different from his brothers and sisters in that he's more of a spy than a fighter. He never uses any strong offensive techniques but he does use illusory spells. He usually observes what the InuYasha gang is doing and then reports back to Naraku. He even says so once that he's not a fighter and his job is to watch. He reports back to Naraku what he's seen.

There are speculations that each incarnation of Naraku is stronger than the last and that since he's the last he's possibly his strongest. He was killed by InuYasha after cutting Kagome. He died with no regrets saying he would have died with Naraku anyway. Because of that cut when Naraku dies Kagome is sucked into a meidou.