"Sorry about this, brother... but your wife is the ultimate slut..." This is the first and last documentary about the director's sister-in-law who decided to appear in an adult video. The director went on a trip to a hot spring with her to see her feelings and body for himself. Her gentle smile as she gradually opens up, her shy behavior in front of the camera, her body that feels pleasure even while feeling a sense of guilt... The time they spend alone together makes her bolder and more slutty...