's Character Page is open. His voice actor is Mutsumi Tamura.
His ability is the EXS of Dark Needles (闇鉤のEXS) called "Chelicerata" (ケリケラータ)
His weapon is the Eight Legs of Shredding (八裂の八脚 , Yatsuzaki no Yatsuashi) also known as the "Predator" (プレデター)
He's a mysterious boy who's always moving around with a girl called Tsukuyomi who has classical aspects in her.
Byakuya himself controls countless long black claws, captures his opponent and uses his creepy power that devours their Existence.
Objective of these two is unknown, but it seems like Byakuya is using his ability is fulfill Tsukuyomi's wish.
"Hollow Night" where many Fake Born gather, they refer to it as the "Nest" and one by one they devour the high-quality Fake Born who get caught in the net they've set up...
His quote says "No need to worry because my life exists for your sake, big sister." so I guess we can assume Tsukuyomi is his big sister...
His Sample Voices:
1. Sorry to rush you, but I'll have you disappear...
2. Come, into my stomach!
3. This is far from a fight. This is simple hunt, a meal... to fill this stomach.
Dengeki scans reveal two of his moves. Special where he slashes with the claws is called "How should I cook you?" (どう料理しよう?) it can be used twice in a row and deals 20 hits if you manage to hit from close enough that all his claws hit. Byakuya's Infinite Worth is called "Become a part of me" (僕の一部になりなよ)
Nanase's special is "Chasing the Réve" (レーヴを追いかけて)... Réve is French for "dream" if I'm not mistaken... Anyways, that move also has two follow-ups: one where she blows the opponent away and another one which is an overhead. Her Infinite Worth is "Atmosphere of the Heavens" (天空のアトモスフィア)