Leicester Maycraft works as an item engineer for the adventurer guild Clan Oasis in Ert'Aria, a port city famed as the "treasury of the world." His parents, Nagan and Shelley Maycraft, hold influential positions; Nagan manages the city's grand cathedral and maintains a friendship with Mise Altoise, creator of the automaton Minette. This family background situates Leicester within the city's nobility, though he earns recognition primarily for his technical expertise and inventions.

He specializes in harnessing Ale (or Eru), a fundamental mystical energy powering the world's technology and magic. Leicester crafts and repairs devices utilizing this energy, frequently working late into the night to fulfill requests. His notable creations include Montecchia, a paddle-like flying staff gifted to childhood friend Carina Verritti, and his personal weapon—a versatile gun-sword hybrid combining bladed and projectile capabilities. His skill extends to improvisation, like enhancing a hedge trimmer with a beam shooter, cementing his reputation throughout Ert'Aria as a reliable problem-solver.

Leicester exhibits patience, compassion, and a steadfast sense of duty. He maintains a calm demeanor while navigating frequent romantic attention from multiple women, including Carina, puppeteer Agnes Boulange, and knight Chelsea Arcot. Prioritizing others' well-being, he becomes fiercely protective of Minette—the automaton who awakens during a meteor shower and immediately identifies him as her "papa" upon first sight. Leicester embraces this paternal role as they investigate her origins.

He demonstrates a selfless commitment to aiding allies and adversaries. Confronting Aberdeen Roland, who seeks Minette's core to save his own automaton sister Miriam, Leicester insists on finding a solution ensuring everyone's safety, embodying an unwavering "save everyone" ethos. This resolve extends to mediating Clan Oasis conflicts, supporting friends like the comedic Tortilla sisters, and participating in city events such as the harvest festival. His actions consistently emphasize teamwork and empathy, reinforcing his role as the guild's emotional anchor.

Leicester's development centers on evolving relationships and responsibilities. Initially focused on engineering and casual questing, his life gains deeper purpose through guardianship of Minette and investigating broader mysteries surrounding Ale energy and automata. He balances these duties while navigating the affections of those around him, remaining mindful of Carina's longstanding feelings and fostering a cohesive, familial dynamic within Clan Oasis.