Nise Shiki (literally Fake Shiki) is the true antagonist of the main story in Tsukihime PLUS-DISC, "Alliance of Illusionary Eyes" (幻視同盟).
Having the ability to "see" into the past of those he passes by, he becomes obsessed with Tohno Shiki after accidentally peering into his memories. He then begins impersonating Shiki and becomes a serial killer, finding life to be meaningless while testing Seo Akira's future predictive ability.
