Blood Plus the Live Action Movie, is mainly about Saya one again. But in a different situation, has some of the same characters, but this time they're all in America.
Saya starts on trying to go to an American High School, just to fit in for a while. To say down-low. While Saya is at this, she not only finds a new family member, but she always finds a new friend.
Yes, it doesn't really relate to the before series. But If you watched the before series, and you just watched the Live-Action Movie now, you will understand it better than others.
It is just Saya in a different situation.
There-for-on, I fully reccomend any anime fans out there, to just go ahead, and try this movie out. Maybe you'll be able to understand the Live-Action Movie if you haven't watched the series before, but thats your risk, and go for it.