There exist in the world monsters called Utsuro, the favourite food of which is the bioenergy nectar, possessed by girls not yet of age. Despite belonging to an organisation called The Garden that works to fight these monsters, Iruka Natsumi lives her life deathly afraid of being eaten by them. Yet then, a girl boasting overwhelming power appears before her! Will they reach the age of nineteen, or will they be eaten by the monsters first!?