— < K > is the first mini album by HeeJin. It was released on October 31, 2023 with "Algorithm" serving as the album's title track. The physical album comes in two versions: A and B.

Heejin's long awaited comebut was finally released after 7 years after her first ever solo promotion! I may dislike Modhaus but they know how to make music for sure, "K" is a beautifully crafted EP and it does not surprise me at all that HeeJin had a part in the development. The music video is fun, the songs are all amazing, and HeeJin seems to be enjoying her promotions! What makes me sad though is when she mentions being alone during music shows... I miss ot12 LOONA T_T

- It's so difficult to pick just one song as a favorite here!!! I was going to pick Video Game, but Algorithm is a perfect title track, ANDD Nokia is so well made!

- Not a typical live performance, but this is my favorite "stage." I hope ot12 visits here one day!