Shin'yû no tsuma: Mikkai no kuro shitagi

Summary

Takamiya and Morimoto were classmates at university. They got along well in many ways, but Takamiya's wife, Madoka, was a domestic housewife, while Morimoto's wife, Miki, was an interior designer with a penchant for extravagance—they were complete opposites. Furthermore, the Morimoto couple were both openly having affairs. One day, while Takamiya was on his way home, Miki approached him under the guise of a coincidence and seduced him…