Due to her husband's exclusive interest in infantile roleplay, wife Hikari finds herself sexually unfulfilled. Into this strained situation returns her flirtatious father-in-law, now living in the same dual-household residence, allowing free movement between their homes. One day, Hikari is caught masturbating by her father-in-law. Though initially shocked and confused by the sudden encounter, she gradually becomes the focus of his growing desire. A forbidden relationship begins to unfold between them.