Finral Roulacase is a member of the Black Bull squad of the Magic Knights in the Clover Kingdom. He is a nobleman by birth, being the eldest son of the prestigious House Vaude, a family known for producing powerful users of offensive spatial magic. However, Finral was unable to master the attack-oriented magic his family prized, as he has a deep-seated aversion to violence and fighting. This led to him being constantly compared, and found wanting, against his talented younger half-brother, Langris. Feeling like a failure and cast aside by his family, Finral adopted a carefree and flippant personality as a way to escape from his feelings of inferiority and the pressure of his noble heritage. He eventually left his family behind, changing his surname to his mother's maiden name, Roulacase, and joined the Black Bulls, a squad known for housing misfits and outcasts.

Personality-wise, Finral is immediately recognizable for his womanizing nature; he is easily distracted by women, frequently flirts, and often abandons his duties to ask out women he has just met. This habit is so pronounced that it interferes with his missions and is a running source of frustration for his captain, Yami Sukehiro. Beyond this superficial flaw, Finral is shown to be a relatively normal, kind-hearted, and considerate individual, especially when compared to the many eccentric and volatile members of his squad. He is also quite cowardly in the early stages of the story, always seeking to avoid dangerous confrontations and complaining when faced with difficult situations. He values his position as a senior member of the Black Bulls and becomes frustrated when his younger squadmates do not show him the respect he feels he is due.

Finral's primary motivation changes significantly over the course of his development. Initially, he is content to simply have fun, run away from his responsibilities, and prove that he is not his brother. He lacks confidence in his own combat abilities, believing his usefulness is limited to his supportive magic. However, after seeing his comrades fight with absolute determination against a powerful enemy named Vetto during the battle at the Seabed Temple, Finral has a revelation. He decides that his goal is no longer to become the strongest individual but to use his unique abilities to make the Black Bulls the strongest squad. This marks a turning point, as he begins to embrace his role as a vital support mage and takes his duties as a Magic Knight more seriously. Later, after the conflict with the elves, he resolves to become a man worthy of his fiancée, Finesse Calmreich, and to compete for the position of head of the House Vaude, which includes making a concerted effort to control his compulsive flirting.

Within the story, Finral serves as the Black Bulls' primary means of transportation and tactical support. His spatial magic is incredibly rare and allows him to open portals for instantaneous travel, which is constantly exploited by Captain Yami, who often refers to him as the "chauffeur" or "errand boy". In battle, Finral seldom engages in direct offense, as he lacks attack spells. Instead, he focuses on moving his allies into advantageous positions, evading enemy attacks, and evacuating civilians or injured comrades. His role is that of an enabler, making the already powerful offensive fighters on his team far more effective and mobile.

His key relationships are central to his character arc. His relationship with Captain Yami is one of begrudging respect; Yami constantly bullies and orders him around but also pushes him to grow and shows faith in his abilities when it matters most. His most pivotal relationship is with his half-brother, Langris. Finral is deeply insecure about being overshadowed by Langris, who openly mocks him. The rivalry comes to a head when Langris nearly kills Finral during the Royal Knights Selection Tournament. Yet, Finral never gives into hatred. Later, when Langris's body is possessed by an elf, Finral risks his life to confront him, ultimately defeating him with a powerful punch and a plea for his brother to "come back," leading to a slow and gradual reconciliation between them. He also forms a powerful bond with Asta, the protagonist. He sees Asta's unyielding determination and zero magical power as a perfect complement to his own supportive, attack-less spatial magic, and he comes to call Asta his "strongest partner."

Finral's development is a journey from running away to standing firm. He starts as a seemingly lazy and unreliable womanizer but evolves into a courageous and dependable Magic Knight who has found his purpose in protecting his found family in the Black Bulls. His abilities, though non-offensive, are remarkable. His primary spell is Fallen Angel's Gate, which allows him to connect two spaces he can see or has marked with his magic, enabling long-distance teleportation. However, he cannot open a portal to a place he has never visited. Another spell is Fallen Angel's Wingbeat, which launches a ball of spatial magic that tracks a target and, upon contact, forcibly teleports them to another location. He cannot use attack magic, a fact he laments, but his mastery of support and mobility magic is so precise and powerful that even formidable enemies have acknowledged his skill. His grimoire contains only these spatial magic spells, which he uses to manipulate the battlefield and ensure his comrades can strike where they are needed most.