The other poster, which is now more popular. I think Lum as the Oni-princess sells the premise better.

The movie is REALLY cool, but the script is messy and it probably would have worked better without the UY branding. It's quite artistic and cinematic, with a very unusual storyline and messy script so it completely alienates the UY fanbase, and people outside the fandom won't see it simply because they think they need to see the rest of the series, or the series doesn't interest them.

I think if it was called "Legend of the Oni Princess" it would probably have more discussion among mainstream film critics.