Airi Mizutani is a cheerful and polite student at Root Academy, recognizable by her brown hair, brown eyes, and glasses, usually seen in her school uniform. As a member of the Puzzle Club, she enthusiastically creates puzzles despite acknowledging her own lack of skill in solving them.

Her character undergoes a significant shift during an encounter with the Orpheus Order. Mizerka, an Order member, approaches Airi at an arcade and gives her an Orpheus Ring. Upon wearing the ring, Airi experiences a dramatic personality change: she becomes highly intelligent and confident, shedding her usual clumsiness. In this altered state, she manipulates Nonoha into a trap designed to lure Kaito into solving a crane game puzzle with strict move limitations.

Under the ring's influence, Airi stubbornly resets the puzzle whenever Kaito nears a solution. She eventually enters a heightened "Orpheus state" and presents an apparently unsolvable puzzle before collapsing. Kaito solves the puzzle, revealing Nonoha was never in any real danger. The Orpheus Ring then breaks, causing Airi to revert completely to her original personality with no lasting effects.

Later, during a puzzle-focused camp, Airi, alongside Miharu, seeks Nonoha's help with meal preparations, demonstrating her return to normal club activities and social interactions.