How do I change japanese to english?

I wish I had an iPod Nano in front of me, but I should still be able to walk you through this.

The easiest thing to do and still keep all of your songs and whatnot (a factory restore will get rid of all of those) is to first find someone with the same generation iPod nano as you. Then, go through all of your menus side-by-side with them. The options in each menu should be in the same order, just a different language. Using their Nano as a guide, make your way through Settings-Languange-English.

Long story short, don't let your friends borrow your iPod :P