Saito is a ronin (students who failed college and are preparing to retake exams), and his neighbor is Sumire, a beautiful, kind woman who always helps and cooks for him. Saito had a crush on Sumire for a long time, but she was currently living happily with her husband, so he had no other intentions. Because the walls were quite thin, every time Sumire and his wife made love, Saito could hear the whole thing clearly, making him even more jealous of Sumire's husband. All the time after that, he always thought about Sumire, and whenever he had free time, he masturbated when he thought of her. One day while he was in the room, he heard Sumire's muffled screams. Rushing out, Sumire suddenly rushed in and hugged him. It turned out that there were cockroaches in her house, and Saito was about to return when Sumire asked him to go inside to help her. She was looking for cockroaches, but Sumire kept showing her round buttocks in front of him, her panties completely exposed, making Saito irresistible. He immediately told his heart, saying that he wanted to have sex with her. Hearing Sumire's answer left Saito in disbelief. She agreed to have sex with him! And their illicit relationship began from there. Whenever Saito felt 'needy', Sumire would come to 'take care' of him so he could focus on his studies...