Adult role-play: Koichi grows suspicious when his best friend Masaru only visits while he is away and his mother acts far too casual about it. Finding her underwear stained with semen confirms that something is wrong. Pretending to leave for a training camp, Koichi hides deep inside a closet and witnesses the truth: Masaru arrogantly commands his mother while she clings to him with tearful eyes, utterly submissive and shamelessly displaying herself. Koichi can only stare, transfixed, as their debauched encounter seems to go on without end.