Poppen-sensei is an assistant professor of biology at Udo University, habitually clad in a walking club track suit and constant slippers due to a past foot injury. He possesses a tendency to drift into vivid fantasies sparked by the natural world.

Unexpectedly transported into a fantastical realm within a riddle book, he maintains composure, quickly deduces his predicament, and remains unflustered. His biology expertise informs his detailed observations of this world's flora and fauna, even when encountering anthropomorphic animals and sentient inanimate objects like discarded clothing performing human roles—entities defying conventional biology.

Progress requires solving sequential riddles. Poppen-sensei approaches this methodically, identifying each riddle before attempting a solution, though this pattern shifts later. The challenges pose minimal danger, sustaining an atmosphere of lighthearted absurdity and gentle humor, with occasional satirical reflections of his ordinary life.

He navigates his circumstances not through brilliance or bravery, but via pragmatic problem-solving and scientific knowledge, steadily advancing through the book's narrative structure.