A mother finally tells her son the truth about the vampire she chose to love. The story of how Midori and Tamaki met is not a flashback, it's the answer to every question Yuuki never knew to ask. This OVA exists to break the premise of the entire series in the most human way possible: by showing that the line between human and devil was never the point.

Yuuki goes to see his mother, Midori, and she chooses to tell him the story of how she first met Tamaki twenty years earlier and how the two of them came to fall in love. This single special episode of Devils' Line is a supernatural romance with touches of action, drama and horror. It never aired on television and was instead packaged with the limited edition of the manga's twelfth collected volume.