High Kick Through the Roof

Ma Dun-tak, who played an unemployed father in Unstoppable High Kick!, cameos as an incredible baseball player who was Bo-seok's rival for Hyun-kyung in college. He obviously lost Hyun-kyung's affections (having never obtained them), but went on to be a star baseball player.

Acquaintance of Shin-ae's when she is addicted to the doll-draw machine.

Park Ji-sung

Himself

A cast-member from the first season; is an engineering student.

Original main character from High Kick!'s first season, Il-woo portrays Jung-eum's first love and the original owner of her dog. Although he left her to ostensibly travel the world, his character suffered from a terminal illness and died.

Jang Jun-hyupChorok Hospital Chief of Surgery.

Ji-hoon's friend.

Ahn Shin-wonJi-hoon's friend.

Lee Yu-riA tough, ulzzang high schooler who crushes on Jun-hyeok. After being rejected by him, however, she persistently pursues him until he desperately has Hwang Jung-eum pose as his girlfriend.

An alum of Hyun-kyung's University, and parody of Queen of Housewives.

Young Jeong Hae-ri

And Jang Han-jun as and Jang Han-junElders who helps Jung-eum and In-na install electronics.

Kim Ja-Ok's junior.

Student

Kwang-soo's friend.

Secretary to Lee Soon-jae, and thus subject to Soon-jae's explosive and smelly gas attacks.

Chorok Hospital head nurse.

Ji-hoon's friend.

Adult Jeong Hae-ri

Bo-seok friend's girlfriend who emigrated to the United States; Ga-eun is Bo-seok's first love.

Lee Na-bongJi-hoon's first love and heartbreak.

(신세경, ) : The series centres around Se-kyung and Shin-ae's involvement with the Lee family. Se-kyung is Shin-ae's highly reserved older sister and finds work as the Lee household's live-in housekeeper after a mad escapade involving her father's debt to some loan sharks. She is diligent and frugal, but also initially lacks aspirations. She is clearly more intelligent than her position allows for and longs to go to school as her peers do. Other characters come to admire her, particularly Jun-hyeok and Julien. She is unaware of most of her virtues (including beauty) and approaches the modernity of Seoul with wide-eyed bewilderment and willingness to try new things. She knows Jun-hyeok's love for her before he reveals it. She does like Jun-hyeok, but she really loves Ji-hoon. Julien also had a crush on her from the beginning, which is revealed later in the series. She eventually quits her job to immigrate to Tahiti with her family, but it was hinted in the last episode that she faced a tragic death along with Ji-hoon who was driving her to Seoul - Incheon International Airport in a car accident as their car slipped due to heavy rainfall.

Shin Shin-ae (신신애, ) : Se-kyung's younger sister. Her bright-eyed enthusiasm earns her top grades at her school, despite her having been living in the backwoods of Taebaek for several years. She has boundless energy and has a close knit, loving relationship with her older sister. She has a charming personality and cuteness that wins over almost everyone she meets, with the notable exception of Hye-ri.

Kang Se-ho (강세호, ) : Jun-hyeok's best friend and high school buddy. Academically gifted and physically fit, he quickly develops a tremendous crush on Hwang Jung-eum and becomes her merely annoying "stalker," often shutting himself in Jun-hyeok's closet during tutoring sessions to just to watch her. He is Jun-hyeok's confidant and encourages him to confess his love for Se-kyung. It was revealed that in the future, he will be married to Hae-ri.

Lee Min-hoMinho, the elder brother of the Unstoppable High Kick Lee family, makes a cameo appearance in the first episode. He and his friend Hyeong-wook are lost in the Taebaek Mountains. They are found and taken in by the Shin family. After developing a close relationship, he takes a picture of them and uploads it to his blog. This allows the loan sharks to find Shin Dal-ho and forces Se-kyung and Shin-ae to run away to Seoul, setting the plot in motion.

One of Ji-hoon's early blind dates, set up for him by Hyun-kyung. Unfortunately, Yeo-eun is exposed to Ji-hoon's less-than-charming social obliviousness as he notes her jaundiced eyes and inquires in public whether her urine is brown and bubbly. Her cameo ends with her furious reaction to Ji-hoon as he ignores her to watch an important baseball game of SK Wyverns.