WOW, just WOW!!! It was so good!! Even though the story is little out of line with the original I really enjoyed it. The fight scenes were awesome and the acting was really good too. (I have a Mizushima Hiro bias!!) I also really liked that they set it in a kinda futuristic Tokyo. I really hope they do a second one!!
I read somewhere that sirens/mermaids sang songs that they heard from sailors on passing ships. I imagine this is what a modern siren would sound like singing this song.