Keena of K-pop act Fifty Fifty speaks to reporters at Incheon International Airport, Thursday. She headed to the U.S. to attend the 2023 Billboard Music Awards. Yonhap

Marking the first anniversary of Fifty Fifty's debut, member Keena showed her appreciation to fans for their support despite a recent contract dispute. She is the only member of the quartet to return to the group's agency, Attrakt, after dropping her legal case against it.

"I want to convey my sincerity with courage," Keena, the only member to celebrate the anniversary, said in a hand-written letter shared on Fifty Fifty's official fan site, Saturday. "I'm sorry to my fans, who must have had a hard time because of my careless behavior. I also want to thank you for trusting me and waiting in uncertainty."

The 21-year-old also reflected on the path she has walked so far to achieve personal growth.

"I have learned, experienced and grown up a lot over the past one year," she recalled. "My fans gave a wake-up call for me every time."

Keena concluded her letter with a promise for the future, stating, "In return, I will make you happy again with my music and performance."

Fifty Fifty arrived on the K-pop scene on Nov. 18, 2022, with the EP, "The Fifty." It rose to stardom with the retro-infused song, "Cupid," landing it on the much-coveted Billboard main singles chart just 130 days after its debut.

The group, however, faced a career setback in June, with all four members — Keena, Aran, Sio and Saena — seeking an injunction to suspend their exclusive contracts against Attrakt. They insisted that the company failed to provide accounting data and neglected the singers' health.

But the court denied the request, and Keena withdrew her appeal. Attrakt later ended its contracts with three other members and is currently considering recruiting new bandmates for Keena.

In the midst of these changes, Keena departed for the U.S. on Thursday to attend the 2023 Billboard Music Awards, which will air on Sunday. Fifty Fifty received nominations in the Top Duo/Group and Top Global K-Pop Song categories.