Don't know any streaming site, but found this search engine that looks for files in megaupload and rapidshare that may be of use to get files quickly:
http://www.megadownload.net/

Haven't tried it fully yet, but I suggest doing a search for 'umai kenichi' to see what you come up with. Be careful of downloading files that are split (those are the ones with file extensions as .001 .002 etc.) because you would need to find all the parts and use a program called hjoin to put it all together. But I see some full files around.

Here's episode 1 for example:
http://www.megadownload.net/download..._82ccd415_.avi