This store is tucked away from the main streets of Chinatown, and not a lot of people are aware of it. Skincare and cosmetics is a gigantic money machine in Asia, and Korean brands such as It's Skin are huge in their home country. Here, these brands are often overshadowed by the local giants (e.g. Sephora).
It's Skin is a reputable skincare shop. You can find there a variety of masks, face cleaners, serums and more, with prices ranging from a few bucks to more than 100$ per product. The shop is rather small and so it their selection, but there's many fun/cute products, like Gudetama (aka the lazy egg with a butt) face masks and what not.
A good place to check if you're an adept of Asian skincare!