Tentang
Orphaned during the Dimensional War, Seul-bi grew up in an organization administered by UNION. She was selected for the Black Lambs after participating in a youth training program for CLOSERS run by the same organization.
Her potential strength may not be quite as high as the other members, but through backbreaking effort and practice she has learned to wield her power quite skillfully. In fact, in this regard, she is rated at least two levels higher than her peers.
It was that assessment that earned her the spot of the leader of the Black Lambs. She is a bit of a perfectionist, though, and this often puts her in conflict with Se-ha.
(Source: Closers HQ Wikia)