Bright and cheerful Miho enjoyed a stable married life, but wanted to learn English for her passion of diving. Worried that she'd lose her personal time once their child was born, her husband agreed to her request. After she began attending English conversation classes, he saw footage on her smartphone showing how closely she interacted with her instructor, leaving him shocked and deeply uncomfortable. Later, although they had planned to have a meal together at the language school, Miho didn't return when the time came and ignored his calls. Overcome by jealousy and anxiety, her husband felt his mind spiraling toward madness.