I knew the manga, so I was ready to be annoyed. Instead I got a story that lives in the same world without touching the original characters at all, and the freedom does it good. Jeong Su-in is a supermarket clerk who gets attacked, and the parasite that tries to take her over cannot complete the takeover. What follows is two beings sharing one body, neither fully in charge, and Jeon So-nee plays both sides of that with real precision. The switch between her and the parasite's blank stare is done with her face, not with effects. Koo Kyo-hwan as Seol Kang-woo is the show's pulse. He talks too much, runs from everything, and turns out to be the person who stays. Lee Jung-hyun's Choi Jun-kyung, leading the team hunting the parasites, is frightening in a calm, practical way that I found more unsettling than the monsters. The body horror is inventive without being gratuitous. Heads unfold into blades, and the fights are staged so you can actually follow them. My one reservation is that six episodes is short. The show raises real questions about what makes a person a person, and then the action takes over before it can sit with them. Fans of the manga's quieter tone may miss it. I finished wanting more, which for a series this compact is mostly a compliment.