Noii is a pale-skinned high school student with short blue hair and brown eyes, typically dressed in a dark grey coat, white shirt, red necktie, and black pants. He lives alone with his father, though suppressed memories eventually reveal both parents vanished under unexplained circumstances a decade prior. Initially appearing ordinary, Noii secretly aspires to join the elite military unit Saber, which combats world-threatening monsters called Disasters.

His routine life shatters with the arrival of mysterious transfer student Motis. Soon after meeting her, he witnesses a Level 5 Disaster threat and its defeat, fueling his desire to fight. His protective instincts surface when he retrieves a dropped phone for classmate Cass, leading to a Disaster confrontation. Noii distracts the monster with a fire axe to ensure Cass's escape. Motis intervenes in Blade attire but is disarmed; Noii seizes her katana and kills the creature. Motis warns him to keep the event secret.

Noii becomes entangled with the private defense organization Blade, developing combat skills to fight alongside Motis against escalating threats. A pivotal revelation shatters his perception: his world is an elaborate virtual construct—a game where humans are players and entities like him are categorized as artificial data or NPCs. This triggers a profound identity crisis. He grapples with discrimination from "real" human players who view NPCs as inferior, questioning the value of artificial life and his own existence. This fuels his resolve to protect his world and its inhabitants, whom he considers real.

His journey involves uncovering suppressed truths about his parents' fate and the origins of the Disasters. These revelations deepen his commitment to defending his reality against both the monsters and the dismissive attitudes of external players. Noii evolves from an admiring student into a determined fighter confronting complex moral dilemmas about reality, discrimination, and self-determination.