After accidentally ending up living with his clumsy and unreliable mother-in-law Rina, son-in-law Hideaki finds himself stepping in when she gets fired from her part-time job due to a mistake. Disappointed by her family and sinking into despair, Rina receives unexpected kindness from Hideaki, who helps her search for new work. But as he spends more time with her, Hideaki becomes increasingly drawn to her soft, voluptuous big tits, and his emotions begin to shift in ways he never expected. As hidden feelings slowly surface in their everyday life, the bond between them grows deeper—crossing boundaries of NTR, incest, and forbidden desire.