In the Kagoshima region of Japan, cats have built their own castles and are engaging in playful territorial disputes. The series centers on Nekotarou, an energetic and greedy feline whose greatest dream is to achieve the relaxed unification of the country. Alongside his serious and dependable partner Goro助, recognizable by his figure-eight shaped mouth, they become members of the Neko Island Castle. Their lord is Neko Mataemon, a caring and level-headed cat who enjoys shopping by mail order.

The story follows the group's lighthearted yet ambitious efforts to conquer various warlords and expand their influence. The narrative plays out across multiple episodes in a short format, blending historical Sengoku period themes with the whimsical behavior of cats. The anime adapts the manga by illustrator STUDY Yūsaku, who described the project as a departure from previous works in the series by introducing a stronger narrative focus on cats nationwide who autonomously build castles and compete for territory. Broadcast as a television series with twelve episodes, each installment runs approximately one minute.