Virus.

A mysterious virus spreads out. Anyone infected feels the emotion of love, and the emotion amplifies until it kills the person in love. The pessimist Taek-seon, who likes nothing in life, is infected, and the researcher Gyun reaches her out to test her the medicine that he's developing. Soon Gyun finds out Taek-seon has special antibody, but Taek-seon slowly feels love to Gyun. Is this a real love or just a virus?