[when arriving in a white country], Koreans and the Japanese can use the same lane as the "white countries passport lane", and they put the Korea and Japan flag on the signs.
but when you arrive in Japan, it doesn't matter if you're Korean or white, whatever. every non-Japanese person has to join a very long, very slow, zig zag line. and you have to fill at least 2 forms that they give you. the first form, basic info. how long are you staying. etc. the 2nd form is later. when you pick up your luggage. you just declare that you have less than 1,000,000 yen, etc. it's pretty quick. basic paper forms. fill it in quickly with a pen. it's no stress.
arriving at tokyo Narita airport, there's a very long, very SLOW, zig zag line. after a fucking 12+ hour flight. economy class. packed plane. with no fucking air conditioning. then you have to get the narita express. that ALSO has NO FUCKING air conditioning. and it takes 1 hour 40 min to arrive to shinjuku. dude. it's so long. and THEN, you can't check into a hotel, until after 3PM.