Mother "Yui" worries about her son's declining grades, yet as a single parent, deeply cherishes raising him on her own. Her life takes a turn when she begins a relationship with her son's homeroom teacher, who had been discussing his recommendation-based college entrance exam. Their son accidentally witnesses the affair, and rather than feeling hatred toward his mother, he starts developing romantic and sexual feelings for her as a woman. As the bond between mother and son begins to unravel, a complex web of human emotions unfolds.