Eighteen, male. Guitarist for the band 'Watermelon Sugar'. Mature, dependable, and admirable. A member of 'Watermelon Sugar'. Exceptionally handsome. Top of his class with excellent grades. School: Seowon Arts High School. He came from the future, the year 2023. He is the son of Ha Yichan and Yoon Cheongah in the 2023 future. He has an older brother, but since everyone except him is hearing-impaired, he is a 'CODA' (Child of Deaf Adults), the only one in the family who can hear. After time-slipping to 1995, he realizes his father Ha Yichan is not yet hearing-impaired and that his father's deafness was acquired, not congenital, so he tries to prevent his father's accident. Since he is the same age as his parents after time-slipping, he speaks to them informally.

Eighteen, male. He starts a band because of Choi Segyeong. Frontman of the band 'Watermelon Sugar'. Choi Segyeong is his first love. An 18-year-old youth who looks like he stepped straight out of a cheerful manhwa. If Eungyeol is Rukawa Kaede, Yichan is Sakuragi Hanamichi, for whom 'the left hand is just for support.' He lives alone with his grandmother, who runs the Snail Boarding House in a college town. A member of the band 'Watermelon Sugar'. School: Baegwang High School. Energetic and bright.

Real name is On Eunyu. Eighteen, female. In 21st-century terms, she was a famous 'ulzzang' high schooler in the Gangbuk area at the time. Known as the cello goddess of Seowon Arts High School for her innocent beauty and elegant, classical aura. School: Seowon Arts High School. She came from the future, the year 2023. Having traveled to 1995, she is pretending to be her mother, Choi Segyeong, who should currently be studying abroad in the US. Unlike her cold-hearted mother, she is energetic and bright. She laughs a lot. She takes medication. She is talented at the cello like her mother, but unlike her mother, she hates it. She dislikes playing the cello due to bad memories associated with it.

Eighteen, female. Major: Fine Arts. She has had a long-time crush on Yichan. A beautiful girl who exudes a cold, aloof, and aristocratic atmosphere. Hearing-impaired. She is bullied for being deaf. Her classmates often badmouth her because she cannot hear. The daughter of a wealthy family, she is congenitally deaf. Her mother is her stepmother. School: Seowon Arts High School. Daughter of the conglomerate 'Jinsung Instruments'. The chairman of the conglomerate is Cheongah's father.

Eighteen, male. Manager of the band 'Watermelon Sugar'. Yichan's childhood friend. The Steve Jobs of the Snail Boarding House. A master of information gathering, networking, planning, and negotiation. A member of 'Watermelon Sugar'. School: Baegwang High School.

Eighteen, male. The genius bassist (in charge of guitar) of the band 'Watermelon Sugar'. He only acts prickly and sensitive when he's doing music. A member of 'Watermelon Sugar'. School: Baegwang High School.

Eighteen, male. Drummer for the band 'Watermelon Sugar'. With the pure intention of making their church praises a bit more exciting and fun, he started looking up music videos of foreign drummers and gradually fell into the world of rock. School: Baegwang High School.

Eighteen, male. Pianist for the band 'Watermelon Sugar'. A talented player who went on an early study abroad program as a classical piano major. School: Baegwang High School.

Eighteen, female. She believes she is Choi Segyeong's only best friend. She hates Yoon Cheongah intensely. School: Seowon Arts High School. The biological daughter of Cheongah's stepmother and Cheongah's half-sister.