Koo Se Mi

Name: Koo Se Mi
Native name: 구세미
Also Known as: Koo Semi, Gu Se Mi, Gu Semi
Nationality: South Korean
Gender: Female
Born: April 10, 2002
Age: 24

Koo Se Mi is a South Korean singer, dancer, former member of CIGNATURE (시그니처), and current member of LATENCY (레이턴시). She graduated from Bupyeong Girls’ High School, and before debuting, she spent time as a trainee at JYP Entertainment and attended Joy Dance Academy.

She debuted in February 2020 as CIGNATURE's main vocalist and dancer with their first single, "Nun Nu Nan Na". Despite receiving positive reviews for their music, C9 Entertainment (C9엔터테인먼트) decided to disband the group in December 2024 after several discussions with each member so they could each pursue their own individual activities.

In January 2026, she re-debuted once again, but now as the bassist of LATENCY, an all-female rock band managed by Oddinary Records (오디너리 레코즈), with their first single "It Was Love".

(Source: MyDramaList) Edit Biography

Year	Title	#	Role	Rating
2024	2024 Idol Star Athletics Championships Chuseok Special Korean TV Show, 2024, 3 eps (Regular Member)	3	Regular Member	7.7
2022	Idol League Season 4 Korean TV Show, 2022, 10 eps (Ep. 9) (Guest)	10	(Ep. 9) Guest	0.0
2022	Secret Airlines Korean TV Show, 2022, 21 eps (Ep. 17) (Guest)	21	(Ep. 17) Guest	0.0
2022	My Boyfriend Is Better Korean TV Show, 2022, 7 eps (Ep. 3-4, 6) (Guest)	7	(Ep. 3-4, 6) Guest	7.7
2021	Gossip Idle Korean TV Show, 2021, 75 eps (Ep. 44) (Guest)	75	(Ep. 44) Guest	8.2
2020	Idol League Season 3 Korean TV Show, 2020, 66 eps (Ep. 61) (Guest)	66	(Ep. 61) Guest	8.4
2020	Eungsu CINE Korean TV Show, 2020, 579 eps (Ep. 317) (Guest)	579	(Ep. 317) Guest	6.0
2020	Hidden Singer Season 6 Korean TV Show, 2020, 16 eps [Panelist] (Ep. 14-15) (Guest)	16	[Panelist] (Ep. 14-15) Guest	7.7
2019	Lunch Attack Korean TV Show, 2019, 890 eps (Ep. 603) (Guest)	890	(Ep. 603) Guest	6.0
2013	After School Club Korean TV Show, 2013, 671 eps (Ep. 416, 443, 500, 559, 591) (Guest)	671	(Ep. 416, 443, 500, 559, 591) Guest	7.8
2011	Weekly Idol Korean TV Show, 2011, 707 eps (Ep. 482) (Guest)	707	(Ep. 482) Guest	8.1