A devil-girl raised by demons falls for a human gangster, and the story actually commits to that love being real. The comedy comes from domesticity colliding with the supernatural, not from the premise itself being treated as a joke. Betty's mission to defeat a demon becomes secondary the moment she chooses Danpei over everything else, and the film trusts you to feel the weight of that choice.
Betty arrives in the human world as a devil with a job to do: hunt down the dangerous demon Lutan. Instead, she meets Danpei, a tough-talking gangster caught in a rainstorm, and something unexpected happens. They fall for each other hard, and soon she's living with him in Tokyo under one roof. The problem is that Betty's supernatural family has opinions. Her grandmother and other demons keep showing up unannounced, treating their apartment like a revolving door and generally making Danpei question his life choices. But the real test comes when the old woman decides to send beautiful nymphs to seduce him, determined to figure out if this human is actually worthy of her granddaughter. Caught between her feelings for Danpei and her original mission, Betty has to navigate a chaotic love story where the stakes involve both a dangerous demon still lurking somewhere and a family that refuses to stay out of her business. Romance and supernatural chaos collide in ways neither of them expected.