Haley and Nick Downes are a happy, successful young couple pregnant with their first baby, but when Nick's father dies unexpectedly, his estranged sister Zara suddenly shows up to town with a diabolical plan in store to make the baby and their father's fortune her own.

With her husband working all the time, Kate is thankful when her brother-in-law David reappears to help out. But she soon realizes that he wants to be the new head of the family, and will do anything to make that happen.

Ha-yeong is a successful psychologist. One day she gets a secretive request from her sister Ha-joo. Apparently Ha-joo's husband Woo-seong is refusing to have sex. Ha-yeong agrees to be their couple therapist but finds out that her brother-in-law actually has sexual desires for her and not her sister...

Jun-woo lives with his brother and his wife. After fighting with his girlfriend, he has a drink with his sister-in-law, local, and consults. Due to his brother's frequent business trips, the lonely brother-in-law seduces Jun-woo to have sex with him.

Tired of married life, the husband turns to his brother-in-law family who is staying at home an a long business trip. The husband, who only washed his fingers for no reason, attracts Casanova to encourage his brother-in-law's affair. In addition, he planned to lay down his brother-in-law's house as bait, but as things went wrong, his wife fell into Casanova's hands. The husband can't let go of his anger. When he confessed that to his sister-in-law and threatened to divorce, she said she would do anything for her good sister. The husband, who suddenly got a double income, slowly zips down, hiding his joy.

Jang-soo and Seong-yeon have been married for about 10 years, but they have an unspeakable secret; Jang-soo's brother, Jae-cheol. Jae-cheol used to go out with Seong-yeon before she met Jang-soo. And although Jang-soo couldn't help but marry Seong-yeon knowing her past, he himself had a young girlfriend named Eun-hye... Jae-cheol was getting along fine with Eun-hye when one day she breaks up with him. The love story between two brothers in "Big Breasted Sister-In-Law" will soon come out.

Min-sang and Yoo-ra is already married for two years. Min-sang lives with his wife Yoo-ra and her sister Yoo-mi. Min-sang used to live alone because his parents died early, and Yoo-ra lived alone with her younger sister after their parents died in an accident. Because of this mutual understanding, when they were introduced to each other through a dating agency, they became attracted to each other, and they even got married... I'm starting to feel more and more like a woman.

An unemployed man. The man has no money and ends up staying with his married older brother's house. His sister-in-law feels sorry for him seeing only playing at home. A man who always watches his sister-in-law's thoughts and actions. Then one day, he found out that his sister-in-law was having an affair and cheating on his brother!! He threatens his sister-in-law about what he found out, so she asks him to keep it a secret and tells him that she will grant all his brother-in-law's requests.

Unlike the massage shop next door that is crowded with customers, Ara's massage shop is quiet without customers. One day, Bomi, the ace of the shop next door, comes to Ara's shop, and she learns the trade secret of her next door shop through Ara. That trade secret...

Twins Tia Landry and Tamera Campbell were separated and adopted at birth. Fourteen years later, they encounter each other by chance at the mall. After the families meet, Tia's widowed father agrees to let Tamera and her single mother move in with them.