Logix Ficsario, known to most as Logy, is a young alchemist who begins the story as an eighteen-year-old government official newly assigned to the development team of the Colseit Branch. He arrives at the same time as his colleague Escha Malier, and together they form the core of the research and development division. Logy is serious, down-to-earth, and methodical, yet he possesses a genuine kindness that underpins his actions. He has a perfectionist streak, often organizing the workshop meticulously and cleaning it from top to bottom, which reflects his disciplined approach to both his work and his personal space.

A prominent physical detail is the burn scar on his right arm, a mark from a traumatic event in his past. That past is closely tied to his motivations. Before coming to Colseit, Logy worked in the Central city as an alchemist specializing in airship engines. He was proud to be recognized for his talents and threw himself into developing a new engine. However, he grew frustrated with his mechanic colleagues, believing they did not understand his work, and began researching in isolation. When his experiment failed, it caused a large fire that seriously injured a close friend. Overcome with guilt, he left Central and requested a transfer to the frontier town of Colseit, seeking a fresh start. This experience shapes his guarded demeanor; he avoids talking about his past and initially struggles with trusting others in collaborative work.

In terms of abilities, Logy is a practitioner of modern alchemy, in contrast to Escha's traditional methods. His most distinctive skill is the alchemic sword, a technique that combines swordsmanship with alchemy. He creates and refines various alchemic blades as a hobby, each one tailored for different situations. This combat alchemy makes him formidable in battle and sets him apart from more conventional alchemists. He also synthesizes items and concoctions, applying his methodical training to solve problems and aid the community.

His role in the story is as one of two protagonists. He and Escha are tasked with exploring ruins, investigating the polluted wastelands known as the Land of Dusk, and undertaking assignments that help the people of Colseit. Over the course of the series, Logy gradually opens up, learning to rely on others and to forgive himself for the accident. His partnership with Escha is central to his development: her cheerful, open-hearted nature balances his serious outlook, and their mutual respect deepens into a close bond. He also builds strong relationships with other members of the development team, such as their supervisor Marion Quinn and the swordswoman Linca, as well as local residents like the automaton Clone and Escha's cousin Awin. Through these connections, Logy moves from a self-imposed isolation to becoming a trusted and integral part of the community, ultimately pursuing the dream of exploring the floating Unexplored Ruins alongside his partner.