Hikari has lived with her husband's parents for three years. After her mother-in-law passed away, she began to worry about her lonely father-in-law. One morning, she accidentally sees him masturbating while calling out her name. This sight excites Hikari and leaves her feeling aroused. From that day on, she can't suppress the aching in her body and starts comforting herself. Then one day, her father-in-law returns home to retrieve a forgotten item and catches her masturbating. From that moment, the two grow closer, engaging in handjobs and eventually fucking. Once the boundaries are broken, they seize every opportunity while the husband is away to greedily devour each other's bodies. And so, their secret relationship continues...