Kitamura, a college student, was hoping to lose his virginity to his girlfriend, Kyoko, but a lack of confidence led to an argument between them. Amidst this, he went for a drive at the invitation of his senior, Nishikawa. Along the way, they picked up a runaway girl named Mari. When Nishikawa attempted to force himself on her, Mari turned to Kitamura for help, and he vowed to protect her. After hearing about Kitamura's troubles, Mari offered to let him use her as a practice partner for sex...