Satoshi came to Tokyo to find a job, he rented an apartment here to live, convenient for working and living. One day when he returned home from work, he saw his neighbor Mizuho Aoyama, who was drunk, lying at the door, no longer knowing how to get home. She was the neighbor's older sister who was already married, whom he had always had a crush on for a long time. Like a miracle, now he could take her into his room to take care of her when she was drunk, he was very polite and did not touch her at all. In the morning, he even brought her water to drink; that thoughtful politeness won Aoyama's affection. Bored with her dull husband at home, Aoyama often found reasons to go to the neighbor's house to play, and gradually, the fire near the straw finally ignited...