Mako Oda, a younger woman who becomes the stepmother to Yosuke after marrying his father, enters the household as the former subordinate of his late father's company. Yosuke struggles emotionally with accepting her as his new mother, especially given her youth and beauty. One day, when a friend visits, Yosuke boastfully claims that Mako only married into the family for the inheritance. Spurred by those words, he impulsively forces himself on her. Afterward, his obsession grows—he begins fixating on her, even sneaking into his father's bedroom to spy. But as Mako becomes aware of his actions, she finds herself silently watching him, her emotions slowly beginning to stir in response.