• Fun and cheerful personality. • Fell in love at first sight with Choi Se-gyeong when she walked into the shop for ice cream while he was working part-time ⬇️ • Likes Choi Se-gyeong. • Student at Baekwang High School. • Contrary to his personality, it is suspected he was abused by his father; he currently lives with his grandmother at her boarding house. ————— Later • Becomes obsessed with the phrase 'VIVA LA VIDA'. • A member of the band 'Watermelon Sugar'. • Becomes aware of Cheong-ah's feelings and they fall for each other. • Loses his hearing due to an accident.

Despite his talent for music, he faces opposition from his father. After showing rebellion for the first time, he visits an instrument shop to sell his guitar. Subsequently, he time-slips into the past. Since both his parents were deaf in his original time, he knows sign language. Eun-gyeol is shocked to see his father, Ha Yi-chan, speaking and hearing in 1995, and discovers that Yi-chan also loves band music. He even gets into fights, screaming at Yi-chan to like Yoon Cheong-ah. While living in the past, Eun-gyeol becomes disappointed by Yi-chan's immature and reckless behavior, eventually fighting with him again and leaving the boarding house.

In the early part of the story, the original Se-gyeong left for the U.S. as history intended, and her daughter On Eun-yu, who traveled back in time, is pretending to be Se-gyeong as if she just returned from America. She plans to connect her mother with her first love as a way to ensure her own existence is erased.