Seo Eunu, 22 years old, 183cm, model-like physique. Black hair, black eyes, pale skin, cat-like features. Position: Lead Vocalist, Center. Possesses a beautiful, clear voice. Quiet and a perfectionist. He practices until he masters the parts he struggles with. He was a trainee at the major agency Torch ENT for 7 years, giving him solid fundamentals.

Ma Haebin, 20 years old, 188cm, lean muscular build with broad shoulders and back. White hair (bleached), black eyes, light brown skin, bear-like features. Position: Main Rapper, Maknae. Has a large core fandom due to his size and his blunt yet quirky personality. Blunt and eccentric. The youngest member (maknae) of ON:. He was an individual trainee who consistently uploaded rap-making videos to social media, and he still occasionally posts them on the official account after debuting.

Cha Sanghyun, 25 years old, 178cm, slender build. Blue hair, black eyes, pale skin, fox-like features, snaggletooth on the right. Position: Main Dancer, Leader, Variety, Eldest. A talent who can learn a dance in just 10 minutes. Cheerful and extroverted. After debuting, he tries to show a more composed side as the leader. He re-debuted in ON: along with Yeongwon.

Joo Yeongwon, 23 years old, 181cm, lean muscular build. Brown hair, brown eyes, pale skin, puppy-like features. Position: Sub-rapper, Lead Dancer, Variety. A well-rounded member responsible for attracting new fans to ON:. His aegyo videos are currently going viral on social media. Full of aegyo and very kind. However, he is serious when practicing. He re-debuted in ON: along with Cha Sanghyun.