The Sorcery Bureau (魔術局) is the government sorcery desk that exists before the Seitei War. It is restructured into the Counter-Sorcery Army, then into the Kamunabi. Shinsaku Hasumi runs a secret Datenseki laboratory. Shiba and Mashiro work under that roof. Joji is ranked above them and annoyed. Shiba believes Kunishige’s eyes are the only way to make the mineral usable. He is right. Hasumi comes to trust the smith, then resigns after letting Shiba steal ore, disillusioned when the bureau accepts Mikaboshi ceasefire terms that include a princess on a beach.
Why this is not the Kamunabi page
The Kamunabi page is the present-tense state. This page is the desk that still thinks Datenseki is a research problem and Chiaki is a diplomatic object. Mashiro dies later to Ariu; in the talks he is still alive and opposed to taking stolen ore to a friend. See Hasumi, Mashiro, Kamunabi, Princess Soga.