Pink Tush Girl(1978)

Yuko's boyfriend dumps her just after they have her first sexual experience, so she runs away from her Tokyo home to the western coast of Japan in order to straighten out her feelings. Following behind her on her journey is her friend Rena, who is trying to track Yuko down and find out if she is all right. As Rena traces Yuko's steps, always missing her by a day or two, she discovers that her friend has decided to drop her inhibitions and begin enjoying herself with every man she encounters.