It's gonna be much harder to learn an East Asian language than another western indo-european language, because obviously these are totally different language systems. And I imagine the beginning phase would be especially painful for a westerner.
Surely you can learn some ABCs by taking courses once in a while, but to really be able to use that language, you may need to devote more time and energy, which are, unfortuanately, very scarce for a Ph.D. student.