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.

The story is set in Hiroshima Prefecture's Onomichi City, where a high school student Nashiko Jippensha was kicked out of her house. Without a place to play with her friends, she learns that the mahjong parlor that her father used to run is now vacant. She fixes the mahjong parlor and turns it into a place where she and her friends can have fun, cook, have tea, and sometimes play mahjong.