For a child, Aoyama possesses knowledge on par with that of an adult. Consequently, classmates frequently tease him about his advanced intellect. He is also enamored with the affable woman he recently met at a dental clinic, whose smile brightened his day. One morning, penguins inexplicably begin appearing around his street. Nobody knows their origin or how they arrived, leaving the town bewildered. Aoyama is determined to uncover the truth, and he partners with his new love in studying the birds. Over time, they discover a hovering sphere which they dub "The Sea," a mysterious object. Anything entering The Sea vanishes, and only the penguins can shatter it. Yet a dreadful force emerges when the penguins act, threatening everything. Penguin Highway follows Aoyama and the woman"s quest to trace the mysterious penguins" source, alongside the numerous obstacles Aoyama confronts during his investigation.