A flame that burns twice as bright lasts only half as long. The same goes for the lives of the young Shinobi. Death comes on quiet soles - for those who are lucky - and for those who are still alive, grief is a constant companion. Ryōbi and Ryōna, two Shinobi sisters of the Hebijo Clandestine Girl`s Academy elite, are only too aware of this, because they mourn their older sister every day.
But when a mysterious phenomenon puts the best of the Shinobi world into a parallel dimension, everything the young ladies know about life and death suddenly turns upside down. The strange world resembles a warm island in summer and the enemies waiting for her there are none other than their beloved miscellaneous.
The mysterious mistresses of the island challenge the girls from the four rival schools to a battle of strength and spirit. They promise that the winning school will not only learn the most secret secrets of the Shinobi legends, but will also have the honor of resting the souls of their lovers forever.