Set eight years after Atelier Sophie and four years after Atelier Firis, the story follows the alchemist twins - the reserved but caring Lydie Marlen, and the eccentric, carefree Suelle Marlen who work alongside their father at the family atelier. But due to his inexperience in alchemy they rarely see any customers. While working to hone their skills, the duo uncovers a mysterious-looking painting, and as they reach out to investigate, the girls are drawn inside a world full of a plethora of rare materials perfect for alchemy.
The player controls Lydie and Suelle Marlen as they travel the world, fight monsters, and take on quests to increase their atelier's reputation. The player can receive "quests" from various NPCs around the game's world, and can unlock various secrets and abilities regarding the mysterious paintings they explore. Combat is turn based, and up to six characters can fight at once, divided into three pairs, each pair composed of an attacker and a supporter.
Source: Wikipedia, "Atelier Lydie & Suelle", available under the CC-BY-SA License.