Promised Blood is a faction in Kamihama City consisting of magical girls. They are the remains of three Magical Girl gangs from Futatsugi City. Due to the work of the Wings of Magius, there was a drought of Witches in all areas outside of Kamihama which ultimately led to a very bloody civil war in Futatsugi City. After lots of fighting, the leaders of the three gangs decided that they needed to unite if they were all going to survive.
They learned about Kamihama's Witch surplus and the Doppel system, and they are currently trying to invade Kamihama with the goal of eliminating its native magical girls and taking the territory and Doppel barrier for themselves. Yuna, in particular, who is one of the leaders of Promised Blood, blames Kamihama for the Futatsugi gang war has become so angry that it has resulted in the change in her appearance.