From Mangascreener:

A tengu is an utterly proud and arrogant creature (so much that the Japanese saying, "to become a tengu," means to preen conceitedly) that is said to steal young children away from their homes. In this story, the fractured and disgraced remnants of the tengu species come together from all over the country to rise up, reclaim their pride, and rule over the nation of Japan, as is their right. What kind of effect will the "Tengu Party" have on the humans of Japan, and more importantly, what exactly makes a tengu?