Today is the day of her only son, Takayuki's, important baseball game. "I have something I can't miss today," Yumi tells him as she sends her husband and Takayuki off, leaving her to stay home alone... That "important thing" is a secret rendezvous with her sex friend, Shinichi. What's more, she chose Yumi's house as the location because she doesn't want to waste even a second of time. Then the doorbell rings and Shinichi comes in. Their "unlimited fuck within the time limit" begins at this moment...