Yabunuma 2: Taninbou ni Nakasareru Kimi ga Itoshikute

Previously... protagonist Tomo and his wife Sakumi celebrated their fifth anniversary. They were a typical couple in the middle years of their relationship. One night Tomo happened to meet Sakumi's boss and began to fantasize about them together. He looked for a way to make them sleep together. When Sakumi found out, she became enraged and moved out.

Two years later... will Sakumi inevitably end up with the boss when that notion ended her marriage?

(Source: dlsite)