http://www13.plala.or.jp/french/uso.htm
apparantly melty blood was also announced on april 1st though.
edit: also, apparantly, the logo image changes to AINTU HEART randomly. Not sure how to induce it.
edit2: Oh, I don’t meet the system requirement either http://translate.google.com/translate?hl=en&sl=ja&u=http://www13.plala.or.jp/french/uso.htm&sa=X&oi=translate&resnum=1&ct=result&prev=/search%3Fq%3Dhttp://www13.plala.or.jp/french/uso.htm%26hl%3Den%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26hs%3Dac5