Tokyo Train Girls 4: Young Wife's Desires (揺れる電車の中で　若妻の焦らされた秘肉) 18 years old

Akiko is the heiress of a lumber business family that spans many generations. She married Hiroshi, a company man, and was leading a plain and happy life. But dark clouds overcast Akiko’s happy life when Hiroshi starts an affair with Michiyo, an underclassman from the school Akiko attended. Then Shinji, who used to work in the family lumber business, enters her life the turmoil of men-women relationships becomes tempestuous.