"Welcome to Venus Vangard. We've been expecting you." Sumire Takahana is a seemingly ordinary schoolgirl cursed with the ability to see malevolent ghosts known as "Viruses." Her life reaches a turning point after an encounter with Lucia Nahashia, a "gothic lolita" monster killer for hire. Unwilling to remain on the sidelines while these "Viruses" prey on the weak, Sumire decides to join forces with the mysterious, eyepatch-wearing Lucia to hunt down these "Viruses" before they can harm anyone else.