Nejiki Mia is a supermarket clerk who has very low self-esteem. She believes she has nothing to offer because she was raised by a toxic parent. She suffered physical abuse at the hands of her father, and even after his death, she lived with her mother who has a strong suppressive personality. She affirms herself for the first time when she falls in love and has an affair with the store manager where she works, who is someone that treats her kindly. However, he decides to leave her after his wife's illness worsens, and Nejiki Mia falls into despair. In order to cheer up her beloved store manager, she begins to take extraordinary actions in order to cure his wife's illness. Her feelings gradually become parasitic, as she progressively gets close to not only the manager's wife, but also his son.