[2] Simoun takes place on the earth-like planet Daikūriku (大空陸, "great sky land" or "heaven's shore").
In Simulacrum, the girls grow up until age of seventeen, when they make a pilgrimage to a holy place known as "the Spring" to select their permanent sex.
The sibyllae can inscribe enormous glyphs known as Ri Mājon in the sky using the Simoun to produce powerful magical effects both for combat and ceremony.
Suffering massive losses in the battle, the pair Neviril and Amuria of Chor Tempest attempt an extremely powerful but extremely dangerous maneuver out of desperation named the Emerald Ri Mājon (翠玉のリ·マージョン, Suigyoku no Ri Mājon); Neviril hesitates after making eye contact with the enemy, and the pair fail resulting in an explosion that takes Amuria with it.
A Plumbish suicide bomber sabotages the peace talks jarring Neviril out of her funk and she agrees to pair with Aer.
In an ensuing battle, the enemy manage to separate Chor Tempest, forcing two of its sibyllae, Limone and Dominūra, to perform the Emerald Ri Mājon in desperation.
The allied Plumbish and Argentum forces demand in their terms that all sibyllae become adults by visiting the holy Spring, thereby no longer being able to pilot Simoun.
Victor Entertainment released two maxi singles that served as theme music for Simoun anime series.
The opening theme, "That Which is Beautiful is Good" (美しければそれでいい, Utsukushi Kereba Sore de Ii), performed by Chiaki Ishikawa, was released on April 4, 2006.
[8] The ending theme, "Song of Prayer" (祈りの詩, Inori no Uta), performed by Savage Genius, was released on April 19, 2006.
[10][11] The album Crystals of Wind (風の結晶, Kaze no Kesshō), performed by Savage Genius, was released by Victor Entertainment on July 5, 2006.
One drama CD titled Aa Uruwashi no Haken OL, Nazenanda Simoun Kabushiki Gaisha (嗚呼麗しの派遣OL、実録シムーン株式会社) was released on October 25, 2006.
[13] It is a comedy set in an alternative universe in which several of the characters wind up in modern-day Tokyo and attempt to start their own company.
A retelling story titled Simoun written by Hashiba Hayase was serialized in Comic Yuri Hime volumes 3–5 (January, April and July 2006).
A PlayStation 2 adventure/simulation game titled Simoun: Rose War ~Ri Mājon of Sealing~ (シムーン 異薔薇戦争〜封印のリ·マージョン〜, Shimūn Ibara Sensō 〜Fūin no Ri Mājon〜) has been released by Marvelous Entertainment.
Erica Friedman, the president of Yuricon and ALC Publishing, named Simoun "Best Yuri of 2006", speaking highly of its soundtrack, artwork, and story.
[18] Similarly, Mark Thomas of Anime on DVD called Neviril's design "unreal", lacking the "natural feel" of other characters but has justified it with the "goddess-like" role she plays in the series.
Friedman criticized the Media Blasters release for having strange romanizations of proper nouns, which were insisted upon by the Japanese owners and for having no insert pictures.
[21] Anime News Network praised the story for not having to rely on its yuri content[20][22] and for being a creative mecha series that provides food for thought.