"Wonder Three" is a science fiction anime series that revolves around three alien siblings—Bokko, Nokko, and Pukko—who are sent to Earth on a mission to assess whether humanity poses a threat to the universe. Disguised as animals—a rabbit, a horse, and a duck—they infiltrate Earth to gather intelligence. Their mission takes an unexpected turn when they encounter Shinichi Hoshi, a young boy who discovers their true identities. Instead of reporting them, Shinichi befriends the trio and helps them navigate human society while keeping their secret.

As the series progresses, the siblings grapple with their mission's moral implications. They witness both the kindness and flaws of humanity, leading them to question their original objective. Bokko, the eldest and most serious, often clashes with Shinichi but gradually develops a deeper understanding of human emotions. Nokko, the middle sibling, is more carefree and curious, often finding joy in Earth's simple pleasures. Pukko, the youngest, is mischievous and playful, frequently causing trouble but also providing comic relief.

The narrative explores themes of coexistence, empathy, and the complexity of human nature. The siblings' interactions with Shinichi and other humans challenge their preconceived notions about Earth's inhabitants. Their mission becomes increasingly complicated as they form genuine bonds with the people they were sent to judge. The series balances lighthearted moments with more serious reflections on the consequences of their actions and the potential for understanding between different species.

Throughout the story, the siblings face various challenges, including encounters with other aliens and internal conflicts about their loyalty to their home planet. The series culminates in a decision that will determine the fate of Earth and their own future. "Wonder Three" combines elements of adventure, humor, and introspection, creating a narrative that is both entertaining and thought-provoking.