Meeting old friends as directors and the ending

Junko's husband is Koichi, they are living a difficult life financially and psychologically as Koichi is unemployed. Junko accidentally met her high school friend, Mizutani. He runs an information technology company and says he will help Koichi and his wife. But his main purpose is different, he wants to steal his old friend and beautiful wife Junko. They secretly made love, cheated on each other many times, and then one time Koichi witnessed it.