Yōsei Teikoku (妖精帝國, lit. "Fairy Empire") is a five-member Japanese musical unit, formed in 1997 and part of Team Fairithm. Their music mixes elements of pop rock and heavy metal. Their works include the theme songs of the anime shows: Mirai Nikki, Magical Pokan, Innocent Venus, Kurokami: The Animation, Seikon no Qwaser, Mai-HiME videogame, and the Tokyo Esp soundtrack. They have released several independent albums and four major release albums with their current publisher Lantis: Gothic Lolita Propaganda, metanoia, Gothic Lolita Doctrine , Gothic Lolita Agitator and Pax Vesania.
Yōsei Teikoku attempts to revive the Request Empire that exists between the human world and spiritual realm --known as "Spiritual"-- through their music. The purpose of their music is "to make humans remember the pure heart inside them that believes in fairies, forgotten before we knew it". "Gothic" and "empire" are key words in their musical ideas.
Yui Itsuki (伊月ゆい, born October 25, year unknown) - vocals, chorus, and lyric writing.,
Takaha Tachibana (橘 尭葉, Tachibana Takaha, born March 25) - guitar, keyboards, composition, arrangement and lyric writing. Has worked with Kukui in the past.,
Nanami (名波, Nanami, born ?) - bass guitar.,
Shiren (紫煉）, Shiren, born march 10) - lead guitar.,
Gight (ガイト, Gaito, born march 20) - drums.,
Relu (?, Relu, born ?, family name ?) - drums.,
Prior to the release of Baptize, Yui and Tachibana were the group's only members. Nanami and Relu have since been added. Later, Shiren and Gight.