On the May 20 episode of Mnet's survival program 'KINGDOM: Legendary War', the main vocals of the idol groups ATEEZ, BTOB, and Stray Kids formed a unit to perform IU's song "Love Poem".

ATEEZ Jongho stated, "My heart fluttered at the thought that we would be able to let viewers listen to our song, and our voice." The three main vocalists, ATEEZ's Jongho, BTOB's Eunkwang, and Stray Kids' Seungmin, chose to perform IU's song "Love Poem", which made many fans excited for their performance. 

The three main vocalists' powerful voices and steady notes filled the stage with deep emotions, and touched the hearts of many viewers.

After the performance, one of the judges on the show commented, "Out of all the performances we saw today, this was the best one". Another stated, "I felt a perfection from this stage. I was able to see that you three were having a full conversation and sharing each others' emotions as you made eye contact with each other. I truly could feel your enjoyment of performing".

Singer IU, who happened to see the broadcast of the performance, also praised the unit group on their cover of her song. She posted a short video clip of the stage on her Instagram story, and wrote, "From the beginning to end, it was just so pretty" and linked the full video of the performance, writing, "You must watch the full version".