He's a vampire of unspecified origin and age. He meets Sho, who at the time is a child and is surprsingly unafraid when he sees what Kei really is.
Sho grows up a bit (Gackt)
Now you see Kei and Sho as small time gansters with their friends. It's all going spiffingly until bad things happen that I will not spoil for you and the others see Kei feeding on a bad guy.
We skip time again and Sho has become a big man about town since Kei left
Kei is in trouble else where and Sho tries to help him, but Kei really just wants to die. He's about to get his wish when more caca hits the fan and Sho calls him for help, so Kei goes back.
More bad things happen to do with gangsters and tragic females and then we get this beautiful shot
The story is actually het with a love interest and all that, but oh the slashy undertones. Kei literally escapes from death to go back to Sho, and not for a moment does the audience doubt that he would.
If you're interested in purchasing it then it can be found here:
Amazon.co.uk for UK peeps and
Amazon.com for US peeps
and it's on YesAsia.com, but you have to search for it.
It's a great movie, I recommend it; great plot and lovely eyecandy :).