In broad daylight, a horrific mass murder takes place, and high school student Mina nearly becomes another victim. She survives only through a desperate heart transplant, but as she tries to return to a normal life, she is alarmed by an overwhelming surge of murderous intent she has never felt before. Unbeknownst to her, the heart she received belonged to Misako Shimizu, the very perpetrator of the mass murder. As Mina begins to transform into someone her parents no longer recognize, they can only watch in confusion and fear while the unstoppable murderous urge continues to grow stronger. This family suspense drama unfolds with Mina caught between her original identity and the violent impulses of her donor, leading to an unprecedented struggle against the killer living on inside her.