I have been using the Clio Waterproof Pen Liner Kill XP for several years.

I bought the Clio Waterproof Pen Liner Kill XP 02 Brown 55ml at Olive Young for 15,000 won. I tried it out after getting a recommendation, and I find myself using it often because it applies smoothly and doesn't smudge much. I really liked that it adheres quickly so I don't have to worry about smudging. It's also easy to draw with, so even those with clumsy hands can draw a pretty eyeliner look.