The Hyakki Gokai is a hyper-stylized, ornate weapon resembling a demonic katana with a curved, single-edged blade that glows with an eerie, supernatural aura. The blade features intricate engravings of mythical creatures and kanji symbols, with a hilt wrapped in dark red leather and adorned with a tassel that emits a faint, ghostly light. The guard is shaped like a demon's maw, adding to its menacing appearance, while the entire weapon pulses with energy, suggesting its powerful, otherworldly origins.