[4][9] @onefive was formed in October 2019 by four graduating members of the Japanese idol group Sakura Gakuin,[10] including Kano Fujihira, who was one of the kawaii metal band Babymetal's three rotating "Avengers" support dancers.

[18] In January 2021, @onefive collaborated with the Japanese fashion brand Apres Jour for the outfits worn in the music video for "BBB".

They were also intimately involved in the production process of the music video, sharing their ideas on hairstyles, makeup, outfits, visuals, and cuts.

[27] All of the songs apart from "1518" had their lyrics primarily written by a female high school student and singer-songwriter called Yura, who was the same age as the members of @onefive.

[31] On February 20, 2022, as the circumstances surrounding the COVID-19 pandemic continued to change, the group was able to hold its first in-person solo concert with an audience, titled @onefive 1st Live: 1518, in Osaka at the Umeda Club Quattro.

[36] @onefive made its major label debut with Avex Trax on November 6, 2022, when the digital single "Miraizu" (未来図) was released.

In addition to digital membership cards, it would grant access to exclusive events, diaries, videos, ticket pre-sales, and other premium content.

[4][9] The concert @onefive Live 2023: Chance×Change, which was held in Tokyo at the Ex Theater Roppongi on April 9, 2023, marked the first time that the audience could sing and cheer out loud, being no longer restricted by the COVID-19 pandemic.

[44] On May 12, 2023, the live-action film adaptation of the manga If My Favorite Pop Idol Made It to the Budokan, I Would Die was released with "Chance" as its theme song.

[40] Their vocals as ChamJam from the film and television drama adaptations were included on the second disc of the two-disc album I Live For You (きみのために生きてる, Kimi no Tame ni Ikiteru), released by Pony Canyon on May 10, 2023.

[45][46] On August 4, 2023, @onefive performed as an opening act at the TGC Teen 2023 Summer fashion festival, which was held at the Yoyogi National Gymnasium.

The group had two performances, first at the "Sky Stage" on the rooftop of the Fuji Television Wangan Studio, and second at the "Heat Garage" at Zepp DiverCity.

The members began modeling for Amazon with seasonal outfits incorporating coats, sweaters, and other winter essentials, while aiming to convey the charm of Generation Z through fashion.

Each of the four members designed their own character: Laa the lion by Fujihira, Babu the chick by Yoshida, Zoey the fawn by Aritomo, and Mimi the rabbit by Mori.

[54] It was announced on December 1, 2023, that @onefive would be a participating artist in the NTV Imaginarium 2023 metaverse festival, which was organized by Nippon TV in commemoration of the broadcasting corporation's 70th anniversary.

The members of @onefive created pieces of pixel art depicting their @chib15 characters for the festival, which were both physically displayed at the exhibition and virtually granted as NFTs to those who purchased tickets to the metaverse venue in Cluster.

"Japanese" emphasizes the cultural origins of the members of @onefive, including practices such as bowing, calligraphy, and ikebana, which they would like to preserve and promote.