Demons’ Bond - The Path of Exile -

It is the Warring States period in Japan. After the passing of Hideyoshi Toyotomi, many warlords started to watch for a chance to be the next ruler of the land. In the midst of time where history is changing with the upcoming battle of Sekigahara where the major daimyos split into Eastern and Western Armies, aiming to fight a decisive battle, there were demons who lived in the shadows of history, avoiding human involvement.

The protagonist is a member of the Ten-Demon Alliance, a coalition of demon clan chieftains. Her duty is to protect Princess Yase, leader of the Ten-Demon Alliance. One day, Princess Yase summons all the Ten-Demon Alliance chieftains across the land. [Spoiler hidden]
This is the story of the demons who ran through the Warring States period, with the heroine having two missions in her mind.

[Taken from Demon's bond wiki]