It's waayy too early in the morning and I'm on my way to Hokkaido for a workshop. To avoid falling asleep on the subway, let me tell you about my main problem with Japanese: similar-sounding words.
Not homonyms; I have no issues with words that sound the same. Context makes it easy to figure out if "hashi" refers to a bridge, chopsticks or the tip of something, just like Swedish "vad" can mean "what", "river ford", "bet" and "lower leg muscle" without anybody becoming confused.
No, my issue is with confusingly <i>similar</i> words. "hibiki", "nikibi", "chikubi", "nihiki" and "bikini" mean echo, pimple, nipple, two animals and bikini, respectively, and mixing them up is potentially embarrassing as well as confusing for everybody.
Or "motomeru", "matomeru" and "mitomeru" - to seek or request; to bring together or collate; and to admit or reqognize. I first learned these three words more than five years ago but I still mix them up (yes, I had to look them up just now). It doesn't help that all three are abstract verbs dealing with the mental state of somebody.
I'm pretty well resigned to go through life confusing myself and everybody around me with this.