Kiri Komori is student number 20 in class 2-He, living as a hikikomori, withdrawing from society into seclusion at home. Her name, derived from "komorikiri," meaning "it stays at home," reflects this trait. She initially isolates entirely within her residence, avoiding school. Her teacher, Nozomu Itoshiki, visits her home with Kafuka Fuura to encourage her return. During this visit, Kafuka mistakes Kiri for a "zashiki-warashi," a protective house spirit. Nozomu's accidental compliment about her hidden beauty sparks her feelings for him. This prompts her to leave home, though instead of normal reintegration, she moves into an unused classroom within the school, establishing it as her new residence.

Kiri possesses long dark hair often obscuring her face and a fair complexion. She is almost constantly enveloped in a large blanket, her primary comfort object; beneath it, her clothing is minimal, sometimes appearing as though she wears only underwear. Her physical measurements are 84/55/84, with a height of 165 cm.

Behaviorally, Kiri exhibits extreme shyness and quietness, interacting minimally outside her secluded spaces. She frequently emerges unexpectedly in confined areas around the school, such as lockers, storage closets, or toilet cubicles, still wrapped in her blanket. Despite her reclusive nature, she shows moments of warmth and care, particularly towards Nozomu and his young nephew, Majiru Itoshiki, assisting in caring for him. Her attachment to Nozomu manifests as possessiveness; she reacts with visible annoyance or agitation when other students, especially Matoi Tsunetsuki, interact closely with him, leading to implied off-air conflicts between Kiri and Matoi. Her role remains consistent as the withdrawn student who transferred her seclusion from home to school, driven by a subtle romantic interest in her teacher and a preference for isolated spaces.