The film follows Aurora, a young girl who believes a monstrous creature living under her bed has killed her parents. Desperate for help, she approaches her mysterious neighbor—known only as Resident 5B—who secretly works as a professional hitman and is rumored to kill “monsters.”
At first, 5B suspects Aurora’s parents were actually murdered by assassins targeting him, and he reluctantly takes responsibility for protecting the girl. As they investigate, dangerous killers and hidden conspiracies begin closing in on them, revealing that Aurora has unknowingly become a target as well.
Their situation escalates into violent confrontations with rival assassins and mysterious agents, culminating in a chaotic battle inside Aurora’s apartment building. During the showdown, the terrifying truth emerges: the monstrous “dust bunny” beneath Aurora’s bed is real—a giant creature tied to Aurora’s imagination and emotions.
In the end, Aurora learns she has the power to control the creature, and she and 5B escape the city together to start a new life, suggesting that the monster may now be their unlikely protector.