Officially appearing in the anime Season 2 Episode 13 : "The Greedy Ones who Cross Borders", during the Autumn Festival on the Musashi, where they made their first public performance. Their whereabouts before these events are depicted more accurately in the four-panel comic strip spin-off manga Kyōkaisen-jō no Horako-san (境界線上のホラ子さん) and the Kyoukai Senjou no Horizon -Kimitoasamade- spin-off light novel series, an eight volumes side-story written by Kawakami Minoru, coupled with the limited edition volumes of the first and second seasons of the anime.
In the manga, they eventually decided to create this group at the instigation of Kimi, who declared: "The three of us are going to form a real, honest-to-goodness band!", shortly before the events of April 20, 1648 TE.
As of this instant, they continued practicing besides their other duties during the main events of the storyline, until Kimi chose to enter them for the Autumn Festival’s Special Stage Opening. This choice was made without consent from neither Asama nor Mitotsudaira, and they only learned about when the other members of the Class 3-Plum encouraged them for the concert. According to Tomo, this news was "Too much of a shock!" for Nate and her.
In the light novels, Tomo was the one who came up with the idea of a band one year prior to the events of the main series after Torii Mototada, former Student Council President and Chancellor of the Far East, asked her to fill in for one of the dropping band on the Musashi's side at the "Gagaku Festival", a joint music festival held in Aki’s Itsukushima Shrine, K.P.A Italia's Headquarters.
Asama had already been asked by Toori if she would be willing to join a band sometimes prior to this. Being asked a second time lead her to finally acknowledge her interest in forming a band and she eventually asked Kimi and Mito soon after.During their performance, the three of them are wearing their own shrine maiden outfit: Tomo with her usual official pink outfit and rabbit-like ornaments, Kimi wearing a dark-blue suit with cat-like hair accessories, and Nate a cyan one with even more exaggerated hairpins which highlights her dog-like side.
Although the three of them can be seen singing along during the Autumn Festival, in the manga, Tomo and Nate were greatly embarrassed to do it when Kimi asked about how they should handle the vocals. At the moment, they chose to let Kimi sing alone, the leader being amused by how the two were not honest with themselves.
- Kimi Aoi (Lead Vocals, with Taiko Drums in the light novels)
- Tomo Asama (Lead "electric biwa")
- Nate Mitotsudaira (Keyboards, Violin in the light novels)
- There’s a notable discrepancy in the formation of the group between how they managed it in the manga and in the anime; Tomo still plays the biwa in the two versions, but Kimi and Nate changed theirs: in Horako, Kimi was originally playing taiko drums alongside her vocal performance, which she left for only singing, and Nate was playing violin, but she is actually playing on a keyboard in the anime. This fact is probably due to the difference of time between the publication of the manga and the diffusion of the anime’s second season, the latter being broadcasted from July 7, 2012 to September 29, 2012, before the end of the original run of the manga (January 2012 – November 2012), in the issues of ASCII Media Works Dengeki G's Magazine.