In Myeongdong, go to Olive Young Myeongdong Town (53 Myeongdong-gil, 1F–2F) or

Central Myeongdong Town (27 Myeongdong 8-gil, M Plaza, B1–3F), open until 10:30pm. My Melody fans can grab the limited green tea cleanser, 150g, with a balm and a headband (600 reviews). Limited sets aren't in every store. They make a nice gift too.