Asahi's husband is working away from home, so she lives with her daughter and her husband. She hasn't been getting enough exercise lately, so she's been doing yoga, when her son-in-law Toshio joins in... Asahi accidentally finds out about his huge cock, and can't stop thinking about it. Her frustrations are piling up, and she can't control herself and ends up fucking him at night. Asahi continues to devour his huge cock, day and night. As she gets carried away by his lewd behavior, Toshio begins to get addicted to his mother-in-law's relentless seduction, and before he knows it, he can't live without her...