Hi, We'll be travelling in South Korea about 13N, 3N=Seoul, 3N=Busan, 3N=Jeju , 4N=Seoul. If we buy KR-Pass for 7-dayPass = 143,900 W,(can use KTX trains to Busan, but it mention "may not be used on subways"... anyone know what is it means? are there many rail company? like in Japan = JR Pass,Keisei,etc. KTX Train to Busan from Seoul Stn = 51,200 W (one way) and from Busan we're plan direct to Jeju Island by Ferry, and back again to Seoul via Mokpo. Is it worth to purchase KR-Pass with that condition, and cat it use in Busan rail?