|Book of the Azure Sky|
|Other names||Buch der blauer Himmel|
|Magic system||Ancient Belka|
|Japanese name||蒼天の書 |
(Sōten no Sho)
|First app.||A's (ep.13)|
The Book of the Azure Sky (蒼天の書 Sōten no Sho, officially/Ger. Buch der blauer Himmel) is the Storage Device used by Reinforce II, similar to how her own master uses the Tome of the Night Sky. Initially, Reinforce II shared the Tome of Night Sky with Hayate. To increase data capacity, a division was needed and that's how the Book was created.
The Book of the Azure Sky ("Buch der blauer Himmel") is named after the Tome of the Night Sky ("Buch der Nachthimmel").
Note that "Buch der blauer Himmel" is not proper German, since "Himmel" ("Sky") is masculine and the name should therefore be "Buch des blauen Himmels". Or, if "Himmel" is meant to be plural, "Buch der blauen Himmel".
About half of the data stored in it are the magic data for unison, Rein herself does not really use it for casting spells. Its role is comparable to an external hard disk drive. Though, it functions well in casting magics and loading data for unison.