Gitei to wakazuma: Kinshin furin (1997)

Yamaguchi Maki felt bored with her husband Koichi's linear, monotonous movements, but she moaned and shook her hips, trying to reach a deeper state of ecstasy. The two had only been married six months...This was the second time Yamaguchi Ryo had met his brother's wife since attending their wedding. Having failed his university entrance exams, Ryo had moved from the Kyushu countryside to attend a cram school in Tokyo, and was now staying with his eldest son, Koichi.