TO1 (Korean: 티오원; formerly known as TOO) (stylized in all caps) is a 10-member South Korean boy group formed by Mnet's 2019 reality show To Be World Klass. The group's final line-up was announced on December 6, 2019, with changes made on December 7. The group debuted on April 1, 2020, and rebranded to TO1 on March 28, 2021.
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