Like Adlez said, a typical DAW will generally allow for midi creation (Mixcraft, FL Studio, Studio One, etc) that you'll be able to port into UTAU. If you already have your lyrics, then hopefully you have an idea of a melody. If you don't have a single clue about music, then I suggest learning some basic music theory - music keys and the notes contained in them (scale) is a start.
http://musictheorysite.com/major-scales/list-of-all-major-scales - this site tells you what notes each key scale contains (includes major, minor, and pentatonic scales) as well as basic music theory for learning sheet music. Even if you don't need to know how to read sheet music (since the piano roll will tell you what note you're on), knowing what key your melody will be in is the first step before you think about the instrumentation that might go around the vocals.
If you'll be using a Japanese bank to Engrish, then I'm willing to help with anything you may need to make it understandable.