Kousaka Mayumi, the sensitive wife who reveled in intense sex with men other than her husband in the previous installment.
She had since quit her job and is living a peaceful life with her husband, Yasutomo.

One day, out of curiosity, the two go to a couples' cafe in search of stimulation.
There, they encounter a man with the air of a host.

Since then, Mayumi's behavior has been strange.
It seems she knew him, but she stubbornly refuses to reveal who he is.

After much deliberation, Yasutomo decides to consult Satoru Shinkai, the man to whom he had previously “lent” Mayumi…

[Translated from dlsite]