'Square' is a region covered in monster-infested miasma. 'Pieces' are people aiming to recapture Square, fighting life and death battles every day with the fate of humanity in their hands. 'Tellus', a boy living in the monsters' den, aims to become a piece with the hope of avenging his parents who were attacked by monsters. 'Rune', a member of the Trick Troupe that take care of Tellus, worries for the reckless kid. But one day, Tellus leaves town and sets out to fight monsters without their knowledge. A monster suddenly appears before him, the very one he swore revenge against for his parents, 'Eques'!! "Everyone who took care of me… I'll save you all for sure!" And so grand quest for revenge begins!