Yumi Kazama's first and last fist fuck! Yumi, a wife, is left to look after her nephew Yoshihiko while her husband is away on a business trip. Having lost patience with Yoshihiko's self-indulgence, Yumi tries to kick him out, but ends up being pushed down by Yoshihiko and his friend Kishida. Yoshihiko, who had always been aroused by Yumi's voluptuous body, tries fist fucking with Kishida, something he has always been interested in. As more and more fingers are inserted into her pussy, she writhes between the pleasure and fear of being toyed with, and finally, his fist reaches Yumi's crotch...