I will start by saying that this is a prequel to the manga the ancient magus bride which any is welcome to read!!!
So I first the OVA information on this series and thought that the art and story line where out of this world. As the series isn't finished yet and the first OVA episode was released on the internet today I can't say for sure what the actual story line is. Obviously it's about a magically special girl and the humanoid creature that takes her in and their future relationship because the title literally is The Ancient Magus Bride. The relationship between the girl Chise and the skull headed Ellias is strangely pleasing to read/watch and I personally can't wait for the rest of the series to progress.