Rin, a housewife celebrating her fifth year of marriage, lives peacefully with her kind and considerate husband Kenichi and his family of four under one roof. However, Rin harbors one secret struggle: her elderly father-in-law persistently directs inappropriate, sexually suggestive glances and remarks toward her. Despite the presence of her mother-in-law, he completely ignores her, fixating his attention solely on Rin with words and actions that secretly excite him. Caught in this tense situation, Rin's emotions begin to waver. A taboo affair drama filled with suspense and thrilling forbidden desire unfolds, delivering an intense, heart-pounding tale of infidelity.