Looking for someone who can read Japanese

[Oniya]

Slightly complicated story here.  I belong to an adult art website (I post M/M fiction there, mostly.) and while I was browsing, I found a submission that appears to be copied from another artist.  The quality of the art seems far too professional for the account holder, and there is a poorly removed set of letters and a date(?) in the corner.  I think I can make out the word Ojitan and the number 20090516.  Google was no help, even with Safe Search turned off.

Much clearer is a set of Japanese characters in the lower portion of the piece.  I have no idea whether these are another reference to the source, or perhaps a signature, or maybe even some kind of caption.  It might even be text that is NSFW, so rather than posting it here, I would prefer to PM a link to anyone willing to take a stab at telling me what it says.  (Link will be to the characters only, not the artwork, as the image itself is in the members' only (very NSFW) portion of the art site.)

[Oniya]

Got an answer.  It was no help in tracking down the original, but I now know how to write Happy Birthday in Japanese.  >_>