Kouji and his wife had a fight, so his wife went back to her hometown. While he was trying to persuade her to come back home, his sister-in-law Mako suddenly came to visit. It turned out that knowing about the Kouji couple's discord, she came to give advice and help them make up. That's what she told Kouji, but Mako's real intention was Kouji's penis! Mako suddenly entered the bathroom while Kouji was still inside, requesting help with washing. At night, Mako entered Kouji's bedroom, using her seductive body to entice him. Despite knowing it was wrong, Kouji couldn't resist this incredibly lewd sister-in-law!