In a world where humans co-exist with Juujin (literally: "beastmen"), genetically mutated animals that have remarkably human-like features with the exceptions of extremities such as tails and ears, Juujin are often found as laborers in the work force or raised in households as pets. That is until a new kind of Juujin appears-- Evolutions, EVOs for short. These Juujin have special magic-like powers that they are using against the human race.

Peke, one such EVO, has been raised with her master Yamato Yamamoto. Yamato's mother works for the Health Care Center-- the only agency with jurisdiction over the Juujin, and has developed a special collar that can seal the EVOs' powers. Having used this collar to control Peke's own powers from going berserk, Peke must now release this power to fight and capture the rampaging EVOs to save humanity and to win her master's love.

Vol.1 contains the extra chapter “Bangaihen: Umi to Neko” (番外編　海と猫)