When the blue moon rises in the sky, don't get hit by the moonlight, or else...

Should the moonlight touch you, you will become a monster.

Two weeks after an incident on a bus, Jangmin receives a warning from his phone: "Direct moonlight will cause symptoms of skin changes, mental distress, etc. To prevent exposure, citizens are forbidden from nighttime activities."

But at nightfall, hundreds of texts invite him to come outside and look at the moon...

A series of bizarre events is about to begin...