Haseul is the third member of Loona. She debuted on December 8, 2016 as a member, and released her solo single album "HaSeul" on December 15, 2016.
She debuted as a member of the group's first sub-unit, LOONA 1/3, on March 7, 2017 with the mini album Love & Live. That following October, HaSeul, alongside fellow members HyunJin and HeeJin, became contestants on the survival show MIXNINE, representing their agency and group. They ranked 4th place in the finale, however, and were eliminated when the boys' team won against the girls', thus ultimately not being able to debut.
She is currently on hiatus for health reasons, and has not participated in the past two comeback periods.
| HaSeul | |
|---|---|
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| Full Name | Cho Ha-Seul (조하슬) |
| Birthday | August 18, 1997 (23) |
| Month | December |
| Color | Green |
| Animal | White Bird |
| Sub-Unit | Loona 1/3 |
| Shape | Square |
| Zodiac Sign | Leo |
| Blood Type | O |


In elementary school, HaSeul participated in her school choir, which ignited her love of singing. As a student, HaSeul studied abroad in Sydney, Australia for a month. In high school, she moved to Colorado, USA, and studied for another year. Upon returning to Korea, HaSeul had to stay an extra year in high school due to her time overseas. HaSeul planned to continue with her studies and go to college to study opera.
This plan changed after she was cast by BlockBerryCreative after participating in a singing contest at the recommendation of her music teacher. She passed her audition and became a trainee at the same time as YeoJin and Choerry, in late 2015 or early 2016. She and Choerry lived near each other and would commute to BlockBerry headquarters together.
It is theorized that, since HaSeul represents the white dove, a symbol of peace, she must choose between peace and harmony or learning the truth about the LOONAVERSE and gaining knowledge. HaSeul chooses truth, and decides to kill the white dove, or kill the peace. As a result, she looses YeoJin, her close friend, when YeoJin gets lost in the forest. We later see in the description of Singing in the Rain, "HaSeul, who always seems to cause rain wherever she goes" this could suggest her sadness towards losing YeoJin, who was like a daughter to her.