Canonically, Mara is not the doublet of Belldandy. Spoilers in white, and not just for the demon's identity: Belldandy's doublet is Velsper, the only Celestial to ever remember who her doublet is. She cursed herself to remember, at the expense of never aging; when asked, she replied "would you want to forget her?" When this was discovered, Hild (making her first appearance in the manga) was extremely displeased... There's also no indication in canon that every Celestial is part of the Doublet System. However, since the memories of who's part of the system are erased, they don't know who's part of the system, so they act as if everyone is for safety's sake.
-Rob Kelk
--
Rob Kelk
"Governments have no right to question the loyalty of those who oppose
them. Adversaries remain citizens of the same state, common subjects of
the same sovereign, servants of the same law."
- Michael Ignatieff, addressing Stanford University in 2012
-Rob Kelk
--
Rob Kelk
"Governments have no right to question the loyalty of those who oppose
them. Adversaries remain citizens of the same state, common subjects of
the same sovereign, servants of the same law."
- Michael Ignatieff, addressing Stanford University in 2012