The second daughter of the Sung family, an 18-year-old sophomore at Ssangmun Girls' High School, she grew up always squeezed between her older sister and younger brother. Her grades are near the bottom, but she has a cool personality and is more interested in fashion, looks, and teen romances than studying. With her excellent fashion sense, talent, and cheerful personality, she is known as the mood maker of Ssangmun-dong and the original fashionista. She loves comedy and dancing and is a bright person who brings laughter to her friends and the landlord, Sung-kyun. However, at home, she is a representative second daughter of Korea who lives under discrimination, inheriting only her sister's clothes and belongings and taking on all the errands. She once liked Sun-woo, mistakenly thinking he liked her.

The eldest daughter of the Sung family and a sophomore in the Mathematics Education department at Seoul National University, she is both the pride and the headache of the family. She has a stubborn personality, doing whatever she wants, and a hot temper that no one can stop when she gets angry. Although she is neurotic and prickly, she is an activist student who participates in demonstrations with burning passion. The fact that she is involved in the student movement is a secret that must never be discovered by her father. She was always top of her class in school, and she constantly bickers with and looks down on her younger sister Deok-sun.

A 17-year-old freshman at Ssangmun High School. As the youngest son of the Sung family, he is the only son who receives plenty of love from his parents. He has an appearance that looks very old for his age, making him look not at all out of place among adults. Between his two strong-willed older sisters, he is a timid coward who constantly walks on eggshells around them. He is a precious youngest son who always receives special treatment from his father, Dong-il. Although he is going through puberty, he has a kind and gentle heart and does not cause worry to those around him.

The eldest son of the Kim family, currently on his sixth attempt at the college entrance exam. He is the family's biggest worry, but he remains indifferent to the stress of the exams. He is more interested in hobbies than studying, and his interests change frequently, but he shows intense focus once he becomes interested. Although he lacks some social skills, he has a gentle and kind personality that never harms others. He suffered from fever and heart disease as a child and underwent surgery; he always lives brightly and bravely for his parents, whose hearts ache as much as his. Later, he meets Deok-sun's friend Mi-ok and falls in love with all his heart for the first time.

An 18-year-old sophomore at Ssangmun High School. The second son of the Kim family, he is nicknamed 'Gae-jung-pal' (Dog Jung-hwan) because of his prickly and blunt personality. A soccer fanatic who loves the sport more than anything, he only smiles brightly and shows off his excellent skills when playing soccer. He grumbles a lot, but he is a classic tsundere style who ends up helping others in the end. He excels in both sports and academics, maintaining excellent grades, but he has no girlfriend due to his abrasive personality. While he constantly teases his friend of 18 years, Deok-sun, he cares for and treasures her more than anyone else. He likes Deok-sun.

An 18-year-old sophomore at Ssangmun High School. He is the student council president and the best model student in Ssangmun-dong, possessing both intelligence and character. He is loved by everyone for his sweet, diligent, and principled personality. At home, he is a kind son who acts as the mood maker. When he is with his friends, he also shows the side of an ordinary 18-year-old high schooler who plays pranks. He has harbored a one-sided love for Bo-ra, the older sister of his lifelong friend Deok-sun, and finally decides to confess.

The late-born youngest daughter of Sun-young, aged 6, she is a cute child who monopolizes the love of the people in the alley. She absolutely adores her older brother Sun-woo and loves singing cartoon theme songs. She is curious and active, playing with anything she can get her hands on and following the people in the alley well.

The only son of the Phoenix Hall jewelry shop, he is South Korea's greatest genius Go player who turned professional at the age of 11. With his extraordinary concentration and effort, he rose to the top of the world and currently holds the number one ranking and prize money record as of 1988. Taek is called the God of Go. However, in Ssangmun-dong, he is closer to a 'god-idiot.' He is so quiet it's hard to hear his voice, and he often spaces out, usually being the last to catch on to things. He can't even cook ramen or tie his own shoelaces. Since Go is the only thing he knows how to do, the neighbors always call him 'Heedong-i' from the Dooly cartoon, someone who always needs to be looked after. He is 18 and does not attend school. He begins to like Deok-sun.

A sophomore at Ssangmun High School, he is the youngest in a family of four older brothers and is called 'Dorongnyong' (Salamander) in the alley. A natural-born dancer with excellent skills, he plays the role of the information source among his friends, sharing various tidbits. He has no interest in studying and his grades are at the bottom, but he is optimistic and quick-witted, making him good at counseling others on their worries. Growing up in a dual-income household, he spends a lot of time alone, but he deeply values his friendship with Jung-hwan, Sun-woo, Taek, and Deok-sun. By the way, his dad is the dean of students at Ssangmun High.