A world covered in a red fog. Inside a decaying building, Rin, a girl with an updo, and Rina, a girl with pigtails, search for water. Just when they were about to report to Ritsu located far away, crisis strikes.

Thanks to Wakaba's quick thinking, Rin, Ritsu, and the Rinas are saved. Wakaba's identity is still unknown, but Rin has him tag along for a little expedition.

Wakaba shows a tremendous interest in Kemurikusa. He learns that there are many different kinds in this world, such as the Kemurikusa he received from Ritsu. The group now heads to Sky Bridge.

The party continues their search for water. They are forced to walk on foot at one point and decide to give water to Midori. But then...

The sisters sleep in the train car in order to rest up. Wakaba goes out alone in search of Kemurikusa, but finds himself lost after getting too caught up in his expedition. Deep inside the building, he sees something unexpected.

The party has finally landed on an uncharted island. The end of the tunnel seems to be a different world from what they are used to. With high hopes, they start to follow the root.

The party decides to move forward. The red fog is thicker than ever, and Rin, Ritsu, and Rina fight against the attacks of Red Bugs. They soon face a grim reality.

Rin, Ritsu, Rina, and Wakaba have come to a new island. The path to their destination proves to be a difficult one, and they decide to come up with a plan for their next course of action.

Rin, Ritsu, Rina, and Wakaba each exploit their unique qualities to fight the Red Bugs, and finally...

Rin and Wakaba see the leaf's memory on their way to the red tree. They see the First Person and...

The party uses all their power to go up against the root. How will the journey end for Rin, Ritsu, Rina, and Wakaba?