Mizuki and her boyfriend Kazuya, about to get married, are a happy couple, but Mizuki has a strong sexual desire and secretly masturbating for her boyfriend's sex. Kazuya, who always dreamed of studying abroad, invited Michael, a black man who took care of him, went to his home and all three of them began to live together. After Mizuki stumbled upon Michael's big cock, she was worried about it to the point of exceeding the limit.