Azul Ashengrotto is a second-year student at Night Raven College, where he serves as the dormitory leader of Octavinelle. He is a merperson from the Coral Sea, where his family runs a famous restaurant, a fact he tends to dislike. As a child, Azul was introverted and had a chubby physique, and his nature as an octopus merperson, complete with tentacles and a tendency to spew ink when crying, made him a target for bullying by his peers. This treatment led him to feel deep insecurity about his original form. In response, he devoted himself to intense study and magical training during middle school, determined to transform himself and gain power over those who wronged him. He attended school alongside Jade and Floyd Leech, who took an interest in him and became his close friends and partners.

In appearance, Azul has silvery-blue wavy hair, matching eyes, and silver glasses. He has a beauty mark below his lip on the left side of his face. His typical attire includes a black fedora with a purple seashell, a white dress shirt, a grey coat over an unbuttoned black suit, a cool-toned scarf, white gloves, and a black cane with a silver octopus-shaped handle.

On the surface, Azul presents himself as courteous, friendly, and helpful, often using polite language and a refined demeanor. However, this exterior masks an extremely calculating, greedy, and cunning personality. He is a shrewd businessman who manages Mostro Lounge, a café located within the Octavinelle dormitory. His primary method of operation involves granting wishes to other students, but always in exchange for their most prized ability or talent, whether magical or physical, such as a singing voice or swimming speed. He constructs his deals with carefully chosen words that leave deliberate "grey areas," ensuring that the terms ultimately benefit only himself. He is highly intelligent, skilled in a wide variety of areas, and possesses a talent for persuasion. He hates relying on luck and will go to great lengths to avoid it, even practicing dice rolls to achieve a desired outcome. He has a strong aversion to being indebted to anyone and refuses help unless it comes in the form of a calculated trade.

The motivation behind Azul's actions is rooted in his painful childhood. His relentless pursuit of knowledge, magical power, and the abilities of others stems from a deep-seated fear of reverting to his former self, which he views as a weak and useless crybaby. He is deeply ashamed of his past, going so far as to edit himself out of old photographs and making a secret contract with the Leech twins to never speak of that time.

Azul's role in the main story is most prominently featured during the events at Octavinelle. He preys on struggling students, including Ace Trappola, Deuce Spade, and Grim, tricking them into signing contracts that bind them to work at Mostro Lounge when they fail to meet impossible conditions. He then coerces the protagonist into a deal for the Ramshackle Dorm. When his collection of contracts is destroyed by Leona Kingscholar's unique magic, Azul suffers a mental breakdown. In his desperation to reclaim what he has lost, he overuses his magic and enters an Overblot state, a phenomenon where a mage is consumed by their own negative emotions and magic. After being subdued by a group of students, he awakens with a new perspective. While he still harbors insecurities, he begins to change his ways, stopping his outright trickery and introducing a points-based system for consultations at Mostro Lounge.

Regarding key relationships, Azul's most significant ties are with Jade and Floyd Leech. They have known each other since elementary school and have been close friends since middle school. They function as a trio, with the twins acting as his supporters, though Azul has stated he has no actual control over them. Despite the seemingly superficial and business-like nature of their interactions, he is overjoyed when they remain by his side after his Overblot. He has a competitive friendship with Idia Shroud, as both are members of the Board Game Club. He has a wary relationship with Leona Kingscholar, holding a grudge against him for destroying his contracts. He is also classmates with Jamil Viper and becomes curious about Jamil's true nature, later helping to expose his schemes during the incident at the Scarabia dormitory.

Azul possesses several notable abilities. His unique magic is called "It's a Deal." With a signed contract, he can confiscate any single ability from the target. If the target fails to fulfill the contract's conditions, they are bound to work for him indefinitely. He can also use his magic without a contract to forcibly take abilities, but this is extremely dangerous and brings him closer to Overblot. He is proficient in standard elemental magic, with a particular affinity for ice-based spells. He can use all eight of his tentacles in addition to his hands for writing and other tasks. He knows how to play the piano and was in a band with Jade on contrabass and Floyd on drums during middle school. He is also skilled in potion-making and speaks multiple languages, including the language of animals.