萊莎是一位住在這個處處受限又無趣的村落，「再普通不過的農家女孩」，只是她對自己的現況並不滿意。某天，她和青梅竹馬蘭托和塔奧一起悄悄坐上小船，前往島的對面，展開了她人生的第一場冒險。在那裡她遇到了一位男人，使用著名為「鍊金術」的神奇力量。受到那股力量吸引，萊莎懇求對方教她鍊金術。就這樣，「再普通不過的農家女孩」變成了「鍊金術士」。跟至今以來的打鬧嬉戲不同，他們就此展開了只屬於自己的「僅限今夏的冒險」——

In order to survive the eventual arrival of the "Dusk End," people of the western reaches of the "Land of Dusk" devoted their efforts to rediscover and recreate lost alchemic technologies. Those technologies were then gathered in the alchemy city known as "Central," where research was conducted on how to halt the advance of the twilight. Having learned the newest alchemic techniques in Central, young alchemist Logy requested a transfer to an understaffed town of Colseit on the frontier to make use of his abilities. There he meets Escha, an apprentice girl assigned to the Development Department. Together, the two make a promise to use their alchemic techniques to bring success to the Development Department.