Venus Versus Virus follows Sumire, a regular schoolgirl who has possessed the ability to see ghosts since childhood. She shares this fact with her friends and family, but they dismiss her claims, assuming she is lying. A chance encounter with a brooch that appears out of nowhere, a monster, and Lucia, a goth lolita monster killer, leads Sumire to make a life-changing decision: to use her ability to fight against these "viruses" that feed on the human race.