Was this the 2005 drama you were looking for, or were you perhaps looking for an update on a more recent web series or the anime ? Mistreated Bride (TV Mini Series 2005– ) - IMDb
The episode title, "Downfall of the Sex Prison, the Beginning of Banquet," suggests a shift from the isolated "prison" of individual manipulation to a collective family descent into their shared darker impulses. Cast and Production Credits mistreated bride ep4 upd
Much of the finale centers on Kouji, the step-son of Sumie. By this episode, both Mitsuko and Sumie are involved in an affair with him. Was this the 2005 drama you were looking