Grimoire (七つの大罪 (グリモワール) gurimowāru; English for Grimoire, Japanese for Seven Deadly Sins): Momiji's weapon is a system consists of seven crystals hovering behind her, giving the impression of a pair of wings.
Momiji's magical weapon appear as seven different colored, each crystal bears the Latin name of a sin in the seven cardinal sins and can shoot out flashes with the corresponding colors. The penetrating beams moves at light speed, making it difficult for a normal human to evade. When the beams hit, Momiji's opponent will be affected by the crystal's special power, which is reducing a sense corresponding to the sin that hit.
Like all magi, Momiji aquired her magical weapon after coming in contact with an OOpart given to her by her younger sister, Haruka. It is only when Haruka was killed that Momiji gained the ability to use her magical weapon.
- Lucifer (superbia(ルシファー) Rushifā; Latin for "Morning Star", Italian for "Pride"): the red crystals that takes away the sense of smell.
- Leviathan (invidia(レヴィアタン) Reviatan; Hebrew for "Twisted", Italian for "Envy"): the orange crystal that takes away the sense of proprioception.
- Satan (ira(サタン) Satan; Hebrew for "The Opposer", Italian for for "Wrath"): the yellow crystal that takes away the sense of sight.
- Belphegor (acedia(ベルフェゴール) Berufegōru; Hebrew for "To Open", Italian for "Sloth"): the green crystal that takes away the sense of hearing.
- Mammon (avaritia(マモン) Mamon; Hebrew for "Wealth", Italian for "Greed"): the blue crystal that takes away the sense of touch.
- Beelzebub (gula(ベルゼブブ) Beruzebubu; Hebrew for "Lord of the Flies", Italian for "Gluttony"): the indigo crystal that takes away the sense of taste.
- Asmodeus (luxuria(アスモデウス) Asumodeusu; Avestan for "Fire Demon", Italian for "Lust"): the purple crystal that takes away the sense of pain.
- Grimiore's true nature as a magical weapon may be that it cannot be utilized until someone close to the user has died.