Renji Hiiragi is the male protagonist of the Night Wizard franchise. As a Night Wizard, he defends the world against extra-dimensional Emulators and their Demon Lords. These duties constantly interrupt his education, resulting in frequent absences and his demotion from third-year to second-year student, earning him the nickname "Falling Man."

Assigned to protect Elis Shiho, a transfer student bearing one of the seven Jewels of Virtue, Renji moves into her home alongside his childhood friend Kureha Akabane. He resides on the balcony to maintain constant surveillance. His primary weapon is a versatile Demon Sword-class artifact.

In battle, Renji is determined, yet he exhibits submissiveness towards female characters, particularly his commanding officer Anzelotte and Kureha. Anzelotte routinely coerces him into missions using a predefined response format, overriding his objections. Kureha manipulates his actions using her knowledge of an undisclosed secret about him for comedic effect. Despite perpetually bad luck, he maintains a protective and good-natured demeanor, especially toward Elis, whom he eventually regards as a niece.

Renji evolves from reluctance about his wizard responsibilities to embracing leadership. Initially desiring a normal school life, he later prioritizes safeguarding allies without sacrifice. This resolve is tested confronting Kirihito (the Gazer), who orchestrates events to awaken the destructive god Shaimaru within Elis. Renji's unwavering support helps Elis reject this destiny. Following Kureha's temporary death and revival, he reinforces his commitment to collective survival over mission expediency.

Beyond the anime, Renji features in the light novel series *Hiiragi Renji to Hougyoku no Shōjo* (Renji Hiiragi and the Girl of the Magic Jewels), focusing on his protective role toward Elis. He also appears in the PlayStation 2 game *Night Wizard The VIDEO GAME -Denial of the World-*.