Actually, you may not have noticed. The appearance of the key and the opening of the imprisoned female body is a metaphor for the intrusion of male sexual organs into females. Moreover, the repeated corporal punishment of beating the back is also the most direct hint to ※. The core of the whole film, the key monster, is actually the inner interpretation of the father to the later tenants and other similar perverted imprisoned mental patients with violent disorders. They all have a sick soul that they can't control. The girls who were imprisoned and killed were all in pajamas or nurse clothes, which also showed the paranoia of this type of mental illness on uniforms.
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