In her 18th year of marriage, Hitomi grows anxious over her husband's sudden coldness. Worried he might be cheating, she secretly copes by masturbating to ease her emotional distress. One morning, her husband's company department chief visits to deliver work documents. His kind and gentle demeanor unsettles Hitomi's emotions. As they discuss her troubled marriage, she wrestles with guilt over infidelity, yet finds herself drawn deeper into a relationship with the department chief. Fearing discovery by her husband yet unable to resist the thrill, Hitomi experiences an orgasm for the first time in a long while. Though she burns the word "infidelity" into her heart, she continues surrendering to her desires.