A story about three sisters struggling to survive in a desolate world surrounded by decaying buildings and red fog. The story revolves around Rin, a girl with an updo. There's also Ritsu, the big sister who has cat ears and is always calm, and Rina, the innocent, cheerful one dressed in a maid's costume. Just what is it that these sisters are after in this mysterious world?
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.
The party is on the move in search of water. The new scenery and objects pique the interest of the ever-curious Wakaba, forcing the Rinas to explain everything. During their journey, they witness something…