Haruka, a real estate company employee, is struggling with work blunders and unrequited love for her senpai who just tied the knot when a mysterious 'meteor' crashes into her window. Out of the debris emerges a man who claims to be the demon king! He shocks her further by insisting she was a saint in a past life, making him her sworn enemy. It all sounds like a plot from a light novel! Watch as this tale unfolds—a former saint turned corporate slave cohabiting with the demon king, who surprisingly becomes an affectionate partner.