Zweilt Guardians are the force opposing the Duras in this series.
Zweilt Guardians are members of the Giou clan who have been gifted with extremely strong abilities. Their tasks are to watch over Yuki and hunt down Duras. It is a rule that Zweilt act in pairs. Each Guardian wears a ring infused with magic, in which his or her Demonbane weapon in sealed. They are much more athletic than normal people and are able to heal quicker.
These are the embodiments of a Zweilt's abilities. Each weapon takes on various shapes depending on the user's preference but all have the common power to defeat Duras.
To preserve their abilities, the Zweilt have been reincarnated over and over for several generations. While most members have been partners in their past lives, occasionally a partner would die in battle like Kuroto's previous partner. There were also Zweilt who would fight alone, like Sairi. According to Tachibana, it is extremely difficult to become a Zweilt Guardian, as one would require an "inborn gift", strenuous training and a strong will to qualify.
The current Zweilt Guardians are:
- In Japanese, Zweilt is written as "hand of admonition"
- On each of the rings that a Guardian wears, "Agla" is inscribed before the Zweilt's name (ie: "Agla Tsukumo" is written on Tsukumo's ring, "Agla Tooko" is written on Tooko's ring, etc.). "Agla" means "Thy might is eternal"