Youjin shared the letter on September 10 via KNK's official fan cafe. The letter reads as follows:
"Hello, this is KNK's Kim Youjin.
First of all, I wanted to tell all of [KNK's fans] Tinkerbell that I am sorry that you waited for me and worried about me for such a long time.
I was so happy to have been able to debut and be active as KNK's main vocal for the past two years.
Ever since I was young, it was a long-time dream of mine, and I wanted to do it better than anyone else.
Those kind of thoughts became a burden, and as I got more frustrated with myself, I started facing psychological difficulties, and in the end, made the difficult decision to leave the group.
I have had time to focus on receiving treatment, but standing on stage and resuming activities again became a very difficult thing to do. I wanted to say that I'm sincerely sorry to KNK members and Tinkerbell for having to make this decision.
In the letter I wrote for our one-year anniversary, I wrote that I was really happy having good times with good people.
I was always happy and will always be thankful for the good times we had together from preparing for our debut to promoting as KNK.
I made a lot of promises with Tinkerbell, and I am really sorry to the members, Tinkerbell, and our staff for not being able to keep them.
I will never forget your support.
Once again, I want to say that I am really sorry to the Tinkerbell fans who supported me and really loved me during my activities, as well as KNK members Seungjun, Insung, Jihoon, and Heejun.
I won't forget the love that you gave me over the past two years, and I will treasure it for a lifetime.
To the Tinkerbell fans who believed in me and waited for me until the end, I'm sorry.
Please always give warm love and support to the KNK members, who understood my decision, and I will support and pray for them.
I am sincerely grateful for the time I had [with KNK.]
I'm sorry, and thank you."