Jean Colbert serves as a professor at the Tristain Academy of Magic, specializing in fire magic and history. His past includes a military career as captain of mage troops under the codename "Flame Snake," where he led a mission to burn Agnès' village based on false plague claims. After discovering the village was healthy, he rescued Agnès, an act that shifted his worldview toward staunch anti-war principles and fueled his envy of Saito's conflict-free world, modern Japan.

Transitioning to academia, Colbert has taught for 20 years, focusing on historical research and scientific innovation. Fascinated by technology from Saito's world, he invented gasoline to power an airplane. He oversaw the summoning ritual where Louise summoned Saito, identified the Gandálfr runes on Saito's hand, and consulted Headmaster Osmond to conceal this discovery due to its Void magic ties. During the Fouquet theft, he coordinated vault security and briefed students on recovering the Staff of Destruction.

In the second season, Colbert revealed his Flame Snake identity to Agnès during an academy invasion. To protect her and atone, he staged his death with Tabitha's magical assistance, making Agnès believe he perished. He disappeared temporarily but resurfaced in the third season to rescue Saito and Louise from Sheffield.

Colbert shares a mentor-like bond with Saito, respecting his insights into technology and non-magical perspectives. Kirche von Anhalt-Zerbst pursues him romantically, often using his first name "Jean," which others rarely acknowledge. A calm, introspective square-class fire mage, Colbert avoids combat due to pacifist convictions. His intellectual curiosity and remorse drive his actions, positioning him as a stabilizing influence and symbol of redemption at the academy.