Byakuya

is Naraku's ninth and final detachment, meant to replace Kagura. His main purpose is to observe InuYasha and Moryomaru's growing powers and report back to Naraku.

After taking the power of one slash of InuYasha's Meidou Zangetsuha, he thinks to himself that the end is near, informing us that he knew he was going to die like the other incarnations. When Shippo sees him take the Meidou Zangetsuha's demonic energy, he is aware, but he doesn't capture Shippo, infact, he informs him that he has a chance to get out of Naraku's body alive. Later, Byakuya slashes Kagome with the blade that contained Meidou Zangetsuha's demonic energy. However, before he gets a chance at a second strike, InuYasha attacks him with his Meidou Zangetsuha and Byakuya is absorbed into it, but not before he states that he has fulfilled his purpose, and that he has no regrets. When Naraku dies, a Meidou appears behind Kagome, due to Byakuya's Meidou Blade.

He appears in manga chapter 433 and episode 4 in final act.

Powers & Abilities
He has an incredible power to create illusions, but has many other powers as well: he can possess people with paper soldiers, summon vines to entrap his enemies, teleport others to different dimensions, detach organs from his body and erect barriers; making him essentially the most powerful of Naraku's detachments. He travels on a giant origami paper crane. He also has an ability to detach one of his eyes, which becomes a flying eye demon, which he uses to spy on his enemies. Naraku can also see what Byakuya sees by touching his eye socket, to which Byakuya finds "disgusting". Byakuya also has a fake sword (it is but a handle). This allows Byakuya's final techinque, in which the handle absorbs the demonic energy (which he used to make his own version of Inuyasha's Meidou Zangetsuha) and slashed Kagome. The purpose of this attack is still unknown as the Meido opened up behind Kagome some time after Naraku was defeated.

Trivia

 * There is strong evidence that suggests that Byakuya might be a moth yōkai. Firstly, Byakuya has many of the same powers as other moth yōkai, such as the creation of illusions, insect control, and nature manipulation. He also bears a close resemblence to other moth demons, such as Gatenmaru and Garamaru, particularly his long hair and colored lips. If this were true, it would be Naraku's first and only incarnation that was a member of a particular subspecies of yōkai; all of his other incarnations (with the slight exception of Goshinki, who was nevertheless just an oni) were standard humanoid yōkai and not aligned with any particular animal-derivation; ironic, considering that Naraku is a spider hanyō.