Nagi Springfield, known throughout the magical world as the legendary Thousand Master, is the father of the series' protagonist Negi Springfield and the central figure whose mysterious disappearance drives much of the story. He is a prodigiously talented wizard whose reputation far exceeds his formal education, as he never graduated from a wizard school and instead taught himself combat magic through experience. His fighting style is that of a magic swordsman, combining swift spellcasting with hand‑to‑hand combat, and he is so powerful that he rarely requires the aid of a partner or a ministra magi. Despite his immense strength, Nagi is portrayed as a playful, easygoing, and cunning individual who often acts with a shrewdness that goes beyond common sense. He possesses a healthy ego, and those who knew him recall him as a kind and humorous man who enjoyed lighthearted banter.

Nagi’s motivations are rooted in his desire to protect the people he cares about and to bring joy to the world. He fought in a great magical war alongside his companions, ending the conflict when he was only fifteen years old. After the war, he gained fame as a hero and was given the title Thousand Master, though the exact origin of the name remains ambiguous—some believe he mastered a thousand spells, while others suggest he formed probationary contracts with a thousand partners. In truth, Nagi admits to knowing only a handful of spells and often reads from his own notes to cast others. Nonetheless, his battle prowess is undeniable, and he is considered one of the most powerful mages of his generation.

Nagi’s role in the story is that of the absent father whose legacy shapes his son’s journey. He disappeared in the year Negi was born, 1993, and most people assume he is dead. However, he reappeared four years later to rescue Negi from a demon attack on his home village, briefly giving his son a magical staff before vanishing again. This single act sets Negi on a quest to find his father and become a Magister Magi. Nagi is the centerpoint of the plot; many characters from the magical world have ties to him, including his former comrades, his wife Arika Anarchia Entheofushia (the last Queen of Vespertatia), and figures such as Evangeline A.K. McDowell and Jack Rakan. His pactio with Albireo Imma, bearing the contract number 1001, remains active, implying that Nagi may still be alive.

Notable abilities include his mastery of both magic and physical combat. He is capable of casting spells at great speed and fighting effectively in close quarters without needing a ministra magi. He won the Legendary Mahora Martial Arts Tournament at the age of ten, twenty‑five years before the current story, demonstrating his exceptional skill even as a child. His magical reserves and combat instincts are such that he can hold his own against entire armies. Throughout the series, Nagi is depicted as a warm, protective, and somewhat roguish father figure who, despite his absence, deeply influences his son’s determination and growth.