It is nice that lots of times you can just take a Japanese phrase and map it onto Korean and have a perfectly grammatically acceptable and natural sentence, but Korean verb inflection seems to be more complicated, and so does the honorific system. From what I remember kinship terms are more complex, because not only is it dependent on the age and sex of the referent, but also the sex of the speaker, so that I would use a different word for my older sister than my sister who's also younger than her would.
One noticeable difference between the two languages, though, is that in Korean people you meet and vehicles you board/enter/etc. are marked with 를, which in Japanese is 窶堙ー. That is, *ツ人窶堙ー窶ーテッ窶堋、 and *窶彭ナステ披?堙ーツ湘ヲ窶堙ゥ are the grammatical Korean forms of ツ人窶堙俄?ーテッ窶堋、 and 窶彭ナステ披?堙可湘ヲ窶堙ゥ (except they're in Korean, of course).