A huge sword wielded by Hishigi. It says that has the ability to perform a slash (up to seven at once) at the speed of light: it fires a large, arch shaped energy projectile to strike a distant target. Despite this attack's name, the general consensus is that it does not move at the speed of light. Hishigi used this against Yuan (another one of Taishirou) and Kyo
The name Hakuya means "White Night" ("a sword moves with the speed of light cutting through darkness", as said by Julian)
It was forged by Julian himself (not surprisingly, being Muramasa's master and Mibu's blacksmith). So Hakuya and Fubuki's sword are not a common swords, because a master swordsman has too much power that a lesser sword just can't take it