Seven months ago, I moved to Busan—the second largest South Korean city and home to millions of impossibly glowy complexions—to teach English at an all-girls middle school. My students can be sassy at times, but their beauty tips are always top notch. Last semester one of my eighth-graders showed up to class with perfectly stained red lips. Technically, they’re not allowed to wear makeup at school but the look was so A+ that I decided to let it slide. In the days following, I started noticing hip kid after hip kid walking around with lips that looked like they’d just devoured a giant cherry ice pop. I soon spotted a poster in a store window that featured a bright pair of the trendy stained lips. Intrigued, I went inside and picked up a tube from the shelf. The label clarified that I was holding a peel-off lip tint. Wait, peel off? A little more perusing through the shop and I realized this is a booming K-beauty category, with options for eyebrows too. You paint …