I haven't had to do this myself but what I think I'd do would be to write up my idea, commission somebody who obviously did really awesome anime art to draw a couple of characters to give a bit of visual appeal, and then present it to the publishing company.

Oh, and thank you for Watching me.

Your welcome >^_^<

It would be helpful to find an artist who was intimately familiar with Japanese folklore, mythology and traditional and modern culture. The anime idea I have is a mix of the street racing culture and Japanese spirits such has Kitsune and Neko. That even if I publish though American agencies, my target audience are Anime and Manga fans both in the state and over seas.
But for copy right reasons I don't want to divulge the details over the internet so quickly.

P.s. Your welcome PalanteanWriter. >^_^<