The Ominous Guest

One day, Young-Jun's younger sister So-Young falls ill with a strange illness after returning from a company retreat. To unravel the strange phenomena occurring to him, Young-Jun seeks out Do-Yeon, a distant relative with psychic powers. However, Do-Yeon pushes Young-Jun away, but something unidentifiable appears before the two. And then, one horrific incident after another befalls these two...! Ghosts chase them, and Do-Yeon's dark past is revealed. What will be the ending for these two? (Source: Ridibooks, translated)