A two-day, one-night trip to a hot spring resort with a middle-aged man and his lover, Yui. Yui, a female college student, starts working as a mistress for a middle-aged man to earn some pocket money and to Yui sexually curious. Today is the first time the two of them meet. The middle-aged man, who is aroused by the nervous Yui, forces his cock into her mouth in the open-air bath. Yui is aroused by his lewd and sticky teasing, and gradually becomes submissive and begins to desire it herself.