I’ve studied a little Japanese, and it’s great fun – especially if you like languages with a non-Latin alphabet… Drawing the kanji and kana is almost like drawing a picture… but the characters are hard to memorize (and I never even got to the hard part of learning the Chinese characters.
Having said that, learning to speak on a basic level was not that hard – not that I remember much. Apparently, Japanese becomes quite difficult at the more advanced levels, in part because of the different social registers you have to learn – that is, different phrases and constructions, depending on the person to whom you’re speaking (a respected elder, a child, etc.).
I have read that there’s a vague connection between Japanese and Korean (though both are considered language isolates, as @hut_of_war indicates), though I suspect that idea would be anathema to speakers of either language.
I think it would be great to really learn either one: Which country would you like to visit? Which culture fascinates you more? Perhaps, first learn one and then the other…