Momo, a high school student in Sorasaki, becomes the newest member of Tsukikage, an intelligence agency working to keep the peace in the city. Tsukikage's nemesis is the evil organization Moryo, and it seems a traitor is feeding them info.

Ryza is an ordinary girl. Tired of boring village life, she escapes the village to gather with her good friends in a secret location to talk of their dreams and plan thrilling adventures. One day, the determined Ryza and company decide to head for the forbidden "island across the shore" as their first exploration trip. Together with the alchemist and other friends they meet there, they have a "summer adventure" that they will never forget.