FictionJunction is the solo project of Japanese composer Yuki Kajiura featuring guests musicians, mainly singers. Historically, works between Kajiura and a vocalist were referenced by adding the singer's name after "FictionJunction". Although both perform under the FJ title and are collaborations with Kajiura, they are separate projects.

Yuki Kajiura had been working on various soundtracks, including one for Mobile Suit Gundam SEED. In 2003, she released the solo album, Fiction.^[1] In 2004, she hired vocalist Yuuka Nanri to sing on some of her tracks, including "Chariot of Dawn (暁の車)" which became a hit. In 2005, she added vocalists Kaori Oda, Keiko Kubota, and Wakana Ootaki, who each have their own project.^[1]

Kajiura does not consider the group to have "members". At Anime Expo 2012, she said: "To be honest, FictionJunction is not a 'group.' FictionJunction is just me. Well, actually, it depends on the music and the song. We have gathered several members and singers from everywhere. We don't have 'member' members. I *am* FictionJunction. But I am 'collecting' all the singers that are powerful and worthy to be in this group. They are true professionals, each individual here. I respect them, and I do look up to them. They have the most beautiful voices, and that's how they're selected."^[2]

With the exception of Yuriko Kaida and Joelle, each vocalist has had her own FictionJunction pre-title. Each vocalist's work is considered an individual project.^[1] Some of Yuki Kajiura's vocalists now go by a capitalized name (e.g. Kaori Oda went by FictionJunction Kaori, but now goes by KAORI). At Anime Expo 2012, Kajiura brought vocalists Kaori, Keiko, Wakana and Yuriko Kaida to represent FictionJunction.^[2][3]

• FictionJunction YUUKA

Yuuka Nanri (南里 侑香, Nanri Yūka, born March 13, 1984), as FictionJunction Yuuka, is Kajiura’s first, longest and best-known collaboration under the FictionJunction name, starting in 2004.^[1] The project was originally titled "FictionJunction featuring Yuuka", but the "featuring" part was later dropped to shorten the name.^[4] So far, they have released several singles and two full-length albums. Yuuka can also be heard in the soundtrack for Madlax.

• FictionJunction KAORI

Kaori Oda (織田かおり, Oda Kaori, born May 5, 1988) joined the FictionJunction project in 2005.^[1] The duo performed two insert songs, "Tsubasa" and "dream scape", which were used in Tsubasa Chronicle. "Calling" was chosen as the ending for the anime series Baccano! and "Hanamori no Oka" (花守の丘, "Hill of the Flower Guardian"), was used in Hokuto no Ken: Toki Den.

• FictionJunction KEIKO

Keiko Kubota (窪田啓子, Kubota Keiko, born December 5, 1985) joined FictionJunction project in 2005.^[1] "Kaze no Machi e" (風の街へ, "To the City of Wind") was used as an insert song in episodes 19 and 21 of Tsubasa Chronicle, and "Nohara" (野原, "Field") was the B-side for the FictionJunction single "Toki no Mukou, Maboroshi no Sora". She was also a member of Kajiura's singing group Kalafina.

• FictionJunction WAKANA

Wakana Ootaki (大滝若奈, Ōtaki Wakana, born December 10, 1984) joined the FictionJunction project in 2005.^[1] They performed two songs for the original soundtrack of Fist of the North Star True Saviour Legend: "Hikari no Yukue" (光の行方, "Where the Lights Are") and the Japanese version of "Where the Lights Are" bonus track.^[5] She sang "Paradise Regained" (an insert song for El Cazador de la Bruja) and in the Pandora Hearts soundtrack. She was also a member of Kalafina.

• Yuriko Kaida

Yuriko Kaida (貝田由里子, Kaida Yuriko) first collaborated with Kajiura for the Noir anime soundtrack, in which she sang the songs that helped launched Kajiura's career: "canta per me," "salva nos" and "lullaby." Since then Yuriko Kaida has provided vocals for many of Kajiura’s works, mainly as background chorus. Kaida became a main FictionJunction vocalist until 2009, upon the release of the album "Everlasting Songs" and the single "Parallel Hearts", lending her voice to “here we stand in the morning dew” and “Himitsu” in "Everlasting Songs" and providing vocals throughout the album. She is the only vocalist in FictionJunction that uses her full name on stage.

• FictionJunction ASUKA

Asuka Kato (加藤あすか, Katō Asuka, born August 28, 1981) performed "Everlasting Song", an insert song from anime series Elemental Gelade. Originally sung in English, "Everlasting Song" was re-recorded in Japanese and released as a single in 2005. It reached No. 53 on the Oricon weekly chart and remained ranked for 3 weeks. She also participated on FictionJunction's 3rd Album "Parade" under her stage name Aira Yuuki.

• Joelle

Joelle Strother (born September 26, 1980) is a singer of Japanese-American ancestry. She joined FictionJunction as a replacement for Wakana (beginning 2019) and has participated in multiple live concerts since 2019 and also recorded studio tracks both as a lead and chorus singer.^[6] In her previous work, Joelle sang as a member of Sound Horizon and Linked Horizon, and she has also contributed vocals to Japanese video game soundtracks (including Final Fantasy XIII-2).

FictionJunction sang a cover of "Gatherway" for the album Harvest, which was arranged by Kajiura and their live guitarist Koichi Korenaga.^[27]