The young wife's descent into temptation begins when her former high school teacher husband lends her out to a true sadist, deepening her entanglement in a cuckold relationship with her NTR-obsessed husband. Further drawn into darkness, she meets the sadist Retsuzui at a chance encounter bar, who plunges her into intense experiences and the pleasure of fist fucking, awakening her inner masochism. Part 4 features the "Adultery Investigation: Married Woman’s SM Hell" chapter, unveiling shocking new developments.