Akihito comes to visit the room where his brother and his girlfriend live. She was planning to go home after eating dinner, but her brother's girlfriend Yui stops her and ends up staying the night. Then, Akihito is attacked by his girlfriend, Yui, right next to her brother who has fallen asleep drunk. And even though she knows she shouldn't, she is entangled in Yui's body and is immersed in her sex when her brother wakes up...!?