Supposedly, "yobai" is a traditional Japanese custom where lovers sneak into each other's rooms for an illicit tryst in the middle of the night. For porn purposes, it's a game where six men are randomly matched up with six women in a dormitory-style setting, and the results are caught on handheld camera, gonzo style. The high point is the scene with pretty, curvy Masaki and the director - she brings in an air mattress and gives him a slippery oil massage as a warm-up to a fun, affectionate coupling. The concept begins to wear thin after too much repetition, however.