"Grand Blues!" is a short-form anime series based on the popular mobile game "Granblue Fantasy." The narrative unfolds in a fantastical world filled with sky islands, airships, and mythical creatures. The story centers on the adventures of Gran, a young skyfarer, and his companions as they journey across the skies in search of the legendary island of Estalucia, a place tied to Gran's father and his mysterious past. Alongside Gran are Lyria, a kind-hearted girl with a deep connection to primal beasts, and Vyrn, a small dragon-like creature who serves as both a guide and comic relief.

The episodic structure of "Grand Blues!" focuses on lighthearted, comedic vignettes rather than a continuous, overarching plot. Each episode features the crew encountering various characters from the "Granblue Fantasy" universe, often leading to humorous or whimsical situations. The series highlights the camaraderie and dynamics between the main characters, as well as their interactions with a rotating cast of allies and adversaries. Notable recurring characters include Katalina, a skilled knight and mentor figure, and Rackam, the crew's dependable helmsman.

The tone of the series is predominantly comedic, with a focus on slapstick humor, playful banter, and exaggerated character traits. Despite its brevity, the show effectively captures the charm and personality of the "Granblue Fantasy" world, appealing to both fans of the game and newcomers. The narrative does not delve deeply into the lore or dramatic elements of the source material, instead opting for a more accessible and entertaining approach. The series serves as a light-hearted companion to the game, emphasizing humor and character interactions over complex storytelling.