There is a common Korean belief that anything plus nine (gu in Korean) is always "cursed" and brings about more hardship than usual, including the ninth year of every decade in one's life.
Gu Kwang-soo is 39 years old. He was once the brilliant PD (production director) of the nation's top live music program. But his fall from grace occurs when members of an indie band he'd cast drop their pants onstage and flash the entire country during a live broadcast (based on a real-life incident on MBC in 2005[2][3][4]). Kwang-soo loses his position and gets shunted to another program, a low-rated trivia quiz show. He is desperate to get married, but his workaholic ways leave him little time to date. Kwang-soo often thinks about "the one who got away," his ex-girlfriend Joo Da-in who left him heartbroken when she suddenly broke up with him one day after publicly rejecting his marriage proposal. When they meet again, Da-in is a single mother whose life revolves around her young daughter Eun-seo, and they've just moved into the apartment one floor above Kwang-soo's. Kwang-soo lives with his superstitious older sister Bok-ja and her three sons, Kang Jin-gu, Kang Min-gu, and Kang Dong-gu.
Kang Jin-gu is 29 years old. He is a tour planner for a large vacation travel agency, and he's self-assured, good at his job, and popular with women. But he starts having to reevaluate his whole future when he falls into a one-sided love for the first time in his life. Jin-gu almost confesses his romantic feelings for his friend and co-worker Ma Se-young, who's from a small town, is outspoken and rough around the edges but very loyal. But apart from his fear of being rejected, Jin-gu learns that his stoic best friend Park Jae-bum also likes Se-young.
Kang Min-gu is 19 years old. He is a hot-tempered high school senior and judo athlete. Min-gu dreams of going to his dream college on a judo scholarship, which means giving his all to win a gold medal in his competitive matches. But an upset stomach during a semi-finals match causes him to lose and poop in his pants, and after that embarrassing episode, his judo ranking drops. Min-gu keeps running into a cute but mysterious girl named Han Soo-ah all over town, and he decides that they're fated to be together. Soo-ah is used to having the entire district's high school boys swooning over her, but Min-gu's sincerity eventually wins her over. But Min-gu doesn't know that Soo-ah's hiding some secrets: her real first name is the country bumpkin-sounding Bong-sook, she's two years older than he is and attends a cram school, and that she was once a legendary cussing, tough, party girl in high school.
Kang Dong-gu is 9 years old. He is a child actor who became famous doing food commercials because of his healthy appetite. Dong-gu suddenly feels threatened when during a movie audition, he loses the role to a new rival child actor named Do Min-joon. He soon finds himself in a career slump, with the other stage parents whispering that since he's growing less cute as he gets older, it's become more obvious that he is not good at acting at all. The precocious Dong-gu has also been secretly dating 8-year-old child actress Jang Baek-ji for the past two years, but Baek-ji dumps him for Min-joon.
