Characterized by its eponymous 'boy next door' image, the group defines their work as easy listening with a thematic focus on daily life.

BoyNextDoor debuted on May 30, 2023, with the single album Who!, which formed the first installment in the First Love trilogy that defined the group's first releases.

[3] Hybe Corporation would later acquire the label as a subsidiary in 2020 and included KOZ in its joint auditions in March 2022.

[20] The group released the promotional single "Fadeaway" on November 7, as the theme for the Naver webtoon Garbage Time.

[30] BoyNextDoor held their first fan meeting, titled "OneDoorful Day", at the Olympic Hall in Seoul from June 1 to 2.

[26] The group released the promotional single "Lucky Charm" on June 29 as part of the original soundtrack for the JTBC television series Miss Night and Day.

[35] The band was represented in a K-pop exhibit at the Grammy Museum in Los Angeles, California, alongside 78 other artists under Hybe and its sublabels from August 2 to September 15.

[41] On October 25, the EP surpassed one million copies in cumulative sales based on YG Plus statistics.

[42] On October 31, BoyNextDoor released a cover of "It's Beginning to Look a Lot Like Christmas" exclusively on Apple Music.

[44] The band will also release a promotional single in collaboration with Warner Bros. to commemorate the 85th anniversary of the Tom and Jerry franchise.

[52] The tracks from the trilogy were largely influenced by rock, teen pop, hip hop, hyperpop, and synth-pop.