Anyone ever play a Japanese RPG with only a japanese to English dictionary?

[Mr Khan]

Zim's got it about right. I would recommend learning the basics of Japanese (try Genki: An Integrated Course in Elementary Japanese volume 1), and then trying to tackle it with a dictionary, but the dictionary will get you nothing if you're starting cold.

Also i'd advise watching an anime series or two, something short, just because the Japanese you'd find in the visual-novel elements (especially any dialogue spoken by characters) is going to be drastically different from the Japanese you'll find in a dictionary or a textbook, and you can get a sense of what you hear or read versus what it means.