Nagisa Shiota

Nagisa Shiota grows up with a demanding, often absent father and a mother who pushes him to live out the life she never got to have, forcing him to learn how to read people's moods carefully just to stay safe at home. That skill, built out of necessity, turns out to make him a remarkably sharp observer and, despite classmates underestimating his slight build and quiet manner, the single most naturally gifted assassin in Class 3-E.

Nagisa keeps a personal notebook where he quietly records every small weakness he notices in Koro-sensei, observations that seem minor at first but later turn out to be exactly what the class needs during their most serious attempt to finally stop him. On the surface, he is calm, friendly, and easy to get along with, but underneath that mild exterior hides a real bloodlust that surfaces clearly during training and combat, and Karasuma notes that when Nagisa's killing intent appears for real, he is no longer just practicing.

His rivalry and friendship with Karma Akabane pushes him to keep improving, even as the two take very different approaches to problems. He eventually finds the strength to confront his own mother and even save her, breaking the unhealthy pattern that shaped his childhood. In the end, it is Nagisa who carries out Koro-sensei's assassination, and seven years later he becomes a teacher himself, choosing to follow in his old teacher's footsteps.