Floyd Leech is a second-year student at Night Raven College belonging to the Octavinelle dormitory. He is the twin brother of Jade Leech, and the two are moray eel mermen originally from the Coral Sea. Floyd stands out with his tall, 191-centimeter frame and has bluish-green hair with a longer, darker strand on his right side. His most distinctive facial features are his heterochromatic eyes, with his right eye being yellow and his left eye olive, as well as his sharp, shark-like teeth. He typically wears his school uniform in a notably loose and rumpled manner, with his shirt unbuttoned, bowtie undone, and his trousers often appearing shorter than his brother's, which makes his purple socks visible. He also wears a single blue diamond-shaped earring on his right ear.

Floyd’s personality is defined by extreme unpredictability and a fickle nature, making it difficult for others to anticipate his actions or moods. He is a hedonist who lives entirely in the moment, pursuing only what he finds interesting and vehemently refusing to engage with anything he considers boring. His demeanor is often laid-back and lazy, but this can shift without warning to a more sinister, terrifying, and even violent disposition. Unlike his twin Jade, who is more polished and deceptive, Floyd is more openly prone to mischief and bullying, often finding entertainment in teasing others regardless of their feelings. He shows affection or interest in people by giving them nicknames based on sea creatures, such as calling Riddle Rosehearts "Little Goldfish," Ace Trappola "Crab," and the Ramshackle Dorm's prefect "Little Shrimp." Despite his chaotic nature, he is a genius who, when motivated, can accomplish almost anything with perfect results; the challenge is maintaining his interest long enough to do so.

Floyd’s motivations are almost entirely self-serving, centered on the pursuit of pleasure and the avoidance of boredom. He works at the Mostro Lounge, the Octavinelle-run café, and assists dorm leader Azul Ashengrotto in his various schemes not out of loyalty, but simply because he finds the activities interesting. He and Jade have stated that they would abandon Azul without hesitation should he cease to be entertaining. Floyd’s role in the story is primarily as a chaotic agent and enforcer. He and Jade act as Azul's subordinates and bodyguards, using their intimidating presence to pressure other students and enforce contracts, such as when they corner the protagonist during the conflict with Azul. Although their loyalty is often questioned, when Azul enters an overblot state, Floyd and Jade work together to battle and subdue him, demonstrating a deeper, if unspoken, bond.

Key relationships define much of Floyd’s behavior. His relationship with his twin, Jade, is a complex and equal partnership. Despite their identical appearance, they have no birth order and operate as counterparts, with Jade understanding Floyd’s moods often better than anyone else. Floyd enjoys provoking Riddle Rosehearts, finding the prefect’s explosive anger amusing; this animosity began on the first day of school when Floyd became fascinated by Riddle's red hair and began playing with it during the opening ceremony. While he claims not to have "childhood friend" memories with Azul from their elementary school days, the three have grown to be close partners, and Floyd has admitted he dislikes making Azul angry. Despite his laziness, Floyd is a member of the Basketball Club, is skilled in music, and has a surprising talent for cooking.

In the Episode of Heartslabyul anime, Floyd appears in cameo scenes, showing him interacting with his brother during daily life on campus, such as eating lunch. Floyd possesses a unique magic spell called "Bind the Heart" (also translated as "Constricting Tail"). This magic allows him to interfere with an opponent's attacks, causing them to veer off course and miss their target entirely, effectively deflecting offensive spells directed at him.