In short: It's a bad story idea...done badly. There's the bones of a plot that is given in an exposition scene that tie everything in this Hot Mess together, but I wouldn't spend much brain power trying to understand it. In short, Evil Devil is trying to destroy the universe, but a young Japanese girl (Sami/Samy/Sammy) unwittingly holds the key to preventing this, as she goes dimension-tripping from Japan to a fantasy land to a sci-fi wasteland, fighting baddies along the way. Don't worry much about the particulars of the plot, because it won't help make thisany better.

By the way it ends, it seems very clear to me, that they intended to use this OVA to "test the waters" to see if there was interest in continuing the story of Samy with future episodes. But they did such a terrible job with this OVA, that it pretty much sank into the morass of low-grade schlock that came out that decade, that it pretty much killed that idea right then and there.

Not only is the story a ugly mess, but by god is the quality of the character designs, artwork and animation crappy as hell. Visually, it's awful from start to finish, and you spend more time marveling at how awful the art is, than you do focusing on the story. They didn't just farm the production of this out to the "B-Team", but probably a few letters lower than that.