Airi Sega is a female character distinguished by waist-length dark-brown hair, usually secured in a ponytail with side fringe strands falling near her shoulders. She possesses gray eyes and a large-breasted figure. Her standard outfit is a school uniform: a white collared short-sleeved shirt, a large red bow in place of a tie, a waist-high skirt extending to her thighs, green socks covering her shins, and brown heeled shoes.

In her sole documented scene, Airi sits at her classroom desk one evening, clutching an unspecified letter. She addresses an unseen viewer, voicing reluctance about fulfilling a prior "show me your panties" agreement. Despite acknowledging her promise, she stands and forcefully shoves her desk aside to comply, her expression radiating disgust. She verbally assaults the viewer, labeling them "a piece of filth" and "utterly pathetic." Following an instruction to turn around and raise her posterior for better visibility, she obeys while asking if her position is correct and repeating her contempt. The interaction ends with Airi lifting her skirt higher and denouncing the viewer as "the worst kind of person."

Her surname "Sega" combines the Japanese characters for "swift current, rapids" (瀬) and "congratulations, joy" (賀).