On December 8, 2016, HaSeul was revealed as the third member of girl group LOONA, and released her pre-debut single on December 15, 2016.

HaSeul is bilingual in English and Korean.
HaSeul was initially preparing to study opera music in college.
Her music teacher recommended her to participate in a teenage music festival; she did not win any awards, but was casted to become a trainee under Blockberry Creative.
In the audition, she got accepted singing IU’s “Friday”.
HaSeul trained for 1 year prior to her reveal single.
Her father has always supported her dream of becoming a Singer.
Her goal is to become a singer who can ring the public’s heart with her music.
HaSeul is the weakest in aegyo, but fans keep asking her to do it.
Both her ears have different shapes.
Her name is an acronym for ‘하늘에서 내려온 슬기로운 아이 (lit.
the wise child who came from the sky)’ (from LOONAbirth profile)HaSeul has a fear of birds.
Birthname: Cho Ha-seul (조하슬)
Birthdate: August 18, 1997 (age 22)
Birthplace: South Korea
Occupation: Singer
Discography: HaSeul” (2016) (pre-debut)