Alright, I reinstalled my PC (with Mint this time). I haven't tested everything, but so far the good news is that Beeper is working with Mint (it didn't with Ubuntu) but I can't figure out how to type in Japanese. I downloaded a bunch of things (fctix?) it tells me that it's working (i.e. I can switch the input method) except that... nope... it's Roman alphabet and only Roman alphabet.
Okay, I'm tired, I'm going to bed.