A year after Shiki Tohno's Mystic Eyes of Death Perception helped end Tsukihime's Serial Vampire Homicide case, rumors of a new phantom killer send him back onto the streets. His patrols cross paths with Sion Eltnam Atlasia, an Atlas alchemist hunting a cure for vampirism who believes Arcueid Brunestud holds the data she needs. As Shiki, Sion, and returning faces like Ciel and Akiha Tohno close in on the killer from different angles, their separate investigations start to collide.