Desperate to support his daughter, single father Sujong accepts a lucrative offer from his former college hoobae, Wumin, to participate in a secret research trial. Blinded by the massive payout, Sujong signs the papers without reading the details.

But the experiment isn't just medical—it's transformative. Waking up to discover his physical anatomy has been altered, Sujong realizes he has unknowingly contracted his body away to Wumin's private experiments.