The Ghost is Ethan, the original Patient Zero. He is bitter, suicidal, and immune to love because he watched his 15th-century wife turn into a ghoul. He pushes Soo-Jin away. But Soo-Jin uses future science in a historical context—distilling antiviral herbs, creating a "cure bomb"—proving she is different from his past loves. A slow-burn "forced proximity" romance develops as they hide in a cave from the time-traveling death squad (who want to prevent Lena from ever discovering the cure).
Both partners were infected and died in a previous outbreak; both reincarnated into new bodies, but the virus re-emerges as a psychic or biological bond. zombie sex and virus reincarnation final kan hot
The most provocative element of the series is the "Final Kan" stage—a process of viral reincarnation. The Ghost is Ethan, the original Patient Zero