Anjjogeul Hyanghae Jinneun Gae

One day, Jeong-Woo can't sleep because he sees a ghost that appears every morning at 3 a.m. and bites his fingernails. Tormented by sleep deprivation and fear, Jeong-Woo tries to figure out when this phenomenon began, and is reminded of an incident that occurred after a drinking party with his childhood friend, Hee-Won.

(Source: Ridibooks, translated)