Moonlight Whispers (1999)

An offbeat study of the adult games that men and women play filtered through the actions of two seemingly innocent Japanese school kids, Satsuki and Takuya, two 17-year-olds who first meet practising kendo but later fall head over heels in love. They then discover the ways they can most exuberantly express their love for one another, no matter how perverse. It all starts with Takuya stealing Satsuki's belongings like socks, secretly photographing her beautiful legs, and... When Satsuki discovers this, she takes revenge by dominating him and forcing him to watch her having sex with a schoolmate...