D.I

Dong In debuted with the boy group GreatGuys on August 25, 2017. In October 2021, Dong In appeared as a contestant on the SBS competitive survival show, Kookmin Singer, as part of GreatGuy's group participation. He, along with his teammates, were eventually eliminated but finished within the 'Top 111' ranks (ranks after 40 for individuals were not assigned).

On January 2, 2024, DNA Entertainment announced that Dong In, along with Han Eul, Da Un, Ui Yeon and Hwal Chan would be leaving the group on February 1 after deciding not to renew their contracts. On December 9, 2025, the group opened a new Instagram account with the name, RE:GUYS, announcing their rebranding. It was also revealed that the group would continue as a seven-member group, including Minki, Yeongki, D.