Marina Hishimori, the swimming club president of a prestigious school. She is beautiful, intelligent, excelling in both academics and athletics, admired by her juniors, and an excellent coach. Such a perfect girl looked down on the male club members who tried to win by using vile means. However, a kouhai she cared for fell seriously ill. The only doctor capable of treating the disease was, to her dismay, the grandfather of a male member whom she despised. In exchange for the expensive treatment, Marina had to agree to a "sex friend contract." Can this noble girl endure the sex friend contract...?!