A package arrives for Eri, a sexless and frustrated mother-in-law. She opens it timidly, and inside is some sexy underwear and a vibrator. Eri uses it without question, as the letter says it's a free trial. However, it's actually a trap sent by her son-in-law Hideki, who wants to make Eri's big breasts his own. Hideki, who is filming the whole thing, approaches Eri's body!