Leonii has seen ATEEZ 2 times.

In 2016, the future leader of the South Korean boy band ATEEZ, Kim Hongjoong, sent a mixtape to KQ Entertainment with a letter stating his appreciation for Block B, a prominent K-Pop group signed by the label. He also expressed his interest in becoming a trainee at the company and soon thereafter became the label's first. Several new trainees were added to the label along with Hoongjong, and, in 2017, they joined together as "KQ Fellaz." On May 18, 2018, the band released its debut YouTube video titled followed by the web series "KQ Fellaz American Training." Less than a month later, the band changed its name to ATEEZ with its debut studio album "Treasure EP.Fin: All to Action" dropped on September 18, 2019. While the COVID pandemic forced ATEEZ to stop touring between 2020 and 2021, the band returned to the road in 2022 with "The Fellowship: Beginning of the End" world tour.