SEE ALSO: Sunmi kicks off her solo debut with '24 Hours' MV

The former Wonder Girls member turned solo artist posted the following letter for Wonderfuls on her official fan cafe in the early morning on the 21st:

"Hello, it's Sunmi. Has everyone been doing well? It's been a long time since I greeted you with a letter so I feel awkward. I wanted to thank all of you who waited for me during the past 3 years and 7 months, so I am sharing this post."

"I'm sure you were surprised by the sudden news [of my debut]. Tomorrow is my first broadcast. My heart is going 'bounce and bounce,' while thinking about meeting fans on stage for the first time in a long time."

"There are a lot of things I want to show and a lot of stories I want to share, but now there is a lot of time for us to meet each other. I will show them to you one by one. I will show my fans that these past 3 years and 7 months have not gone to waste."

"See you tomorrow<3."

Get ready for Sunmi's solo debut with "24 Hours" on 'M! Countdown' on the 22nd!