Recently, a reader who shall stay anonymous asked wrote this:
E-mart usually has basil when it is in season. I'm not sure if they have it now since it is so cold. Usually they'll have fancy (curly) parsley. I've found that in Itaewon, the Foreign mart will almost always have cilantro and they often have basil, mint, and rosemary. They also have fresh kaffir leaves, Thai bird chili peppers, and lemongrass. Hannam Market is also pretty reliable for herbs and I have even seen fresh thyme there, but the prices are often ridiculously priced. In the spring I recommend you buy the potted ones. They often run 2-3 housand and if you take care of them, they'll last a while.
Thanks for reading and happy holidays!