Hatsune Miku was officially released on August 31, four years ago, as a singing synthesizer with female persona.
So … why 20th birthday instead of 4th? Well, when she was released back then on 2007, her personal data sheet mentioned that her age is 16, hence she turns 20 today. Apparently, as a virtual idol, Miku is forever 16, hence the correct statement is: Happy 4th Anniversary, Hatsune Miku! ^^
In order to celebrate Miku’s birthday, I have setup a simple, quick party for her earlier. Well, I apologize for the simple party – I promise to organize a proper party next time. XD