Uwakizuma: Nureta W furin(2006)

Keita and Kasumi, and Jin and Emi, were seeing each other again for the first time in a long time at a mutual acquaintance's wedding. They had all known each other since before their marriages, and their initial encounters were also related to each other. However, Emi and Keita were actually an adulterous couple who had been having an affair since before their marriages…