Lead Shax, also known as Shax Lied or Shax Reed, is a student at Babyls, the demon school in the demon world. He is a member of the Misfit Class, the same class as the protagonist Iruma Suzuki. He comes from the Shax family and is the eldest son. His background includes being placed in the Misfit Class after causing a gambling-related incident during his entrance to the school.

Shax has a laid-back and playful personality. He is a compulsive gambler and enjoys video games, often playing during class. He loves the thrill of deception and high-stakes situations, finding excitement in dangerous games and wagers. His typical posture involves sitting cross-legged while floating above the ground using his tail, which he does partly because he is self-conscious about his short stature. He keeps his eyes closed most of the time, which is a habitual trait.

His primary motivation is the pursuit of excitement and the satisfaction of winning. He craves the adrenaline rush of a gamble and enjoys tricking others. Beneath this, he values his friendships deeply and is a loyal classmate. He is also motivated by a desire to become stronger and more recognized, especially after earning the title of Young King. He has a hidden romantic interest in his classmate Elizabetha, though he is too timid to act on it, adding a layer of vulnerability to his character.

In the story, Shax serves as a supporting character and a mood maker in the Misfit Class. He frequently teams up with his close friend Andro M. Jazz, whom he affectionately calls Jazzy. He becomes particularly important during the Harvest Festival arc, where he partners with Iruma. Together, they discover the Legend Leaf and win the festival, earning the prestigious title of Young King, which marks him as a candidate for the future demon king. This event significantly raises his status and rank. He also participates in other school events such as the Music Festival and the Heartbreaker exam.

Shax has strong relationships with several characters. He is especially close to Iruma, whom he considers a younger brother figure, though their dynamic often involves playful banter about who is the actual younger sibling. He is a close friend of Andro M. Jazz, and the two often cause trouble together. He also forms a pact called the Boku Alliance with Purson Soi due to their shared use of the first-person pronoun boku. He has a complicated relationship with his older sister Shaxie, who is overly forward and causes him embarrassment. He is also connected to the Game Batra (game club) and its advisor Orias Ozwell, whom he once challenged and defeated with Elizabetha's help.

Over the course of the series, Shax develops from a carefree gambler into a more reliable and courageous demon. His partnership with Iruma during the Harvest Festival forces him to take responsibility and work as a team, leading to genuine growth. He learns to trust others and to use his abilities not just for personal thrill but for the benefit of his friends. His rank progresses from Aleph to Bet, and eventually to Daleth, reflecting his increased competence and recognition.

Shax's notable ability is his bloodline magic, called Controller or Sense Thief. It allows him to steal any of the five senses of a target, such as sight, hearing, or touch. The stolen sense appears as a dark discoloration on the affected area. He can use this ability offensively to disorient opponents in combat or games. With focus, he can expand the range of his theft, and he can also deploy his magic over a wide area for detection purposes. He also has a familiar called the Clever Monkey, which aids him in certain situations. His gaming and gambling background gives him sharp strategic thinking and calmness under pressure.