Hello Gugudan Semina! Gugudan Semina(구구단 세미나) is one of the official sub-units of the group Gugudan. The group is composed of 3 members Nayoung, Sejeong, and Mina. The name comes from the beginning letters of all their names combined SeMiNa. The group debuted under Jellyfish Entertainment and debuted on July 10 2018. They debuted with their title track MV SeMiNa. The leader of the group is Nayoung. The subunit officially disbanded on December 31, 2020, following the gugudan's disbandment.