Hades Aidoneus is the Greek god of the underworld, a central figure in the story known for his somber demeanor and profound sense of isolation. He is the older brother of Zeus and the uncle of Apollon, placing him among the more senior divine figures in the narrative. Physically, Hades is depicted as a tall young man with a pale complexion, dark green wavy hair that reaches his shoulders, and pointed ears. In his human form, he typically wears the standard school uniform, but his divine nature is revealed through a distinctive red eye and a shift in appearance that includes a crown of thorns and a black robe that evokes the depths of the sea. A skull necklace with a garnet gem serves as a limiter for his divine powers.

The core of Hades's personality is defined by a deep-seated belief that he is cursed and brings misfortune to anyone who draws near. This belief stems from his role as the ruler of the underworld, where the grudges of the dead have attached to him, creating an aura of ill luck. In an effort to protect others from this perceived curse, he maintains a quiet and distant demeanor, often isolating himself from those around him. This self-imposed exile has made him appear cold and unapproachable, but underneath this exterior, Hades is inherently soft and kind. He is shown to be shy, easily flustered, and capable of great warmth once his walls are lowered. In stark contrast to his gloomy self-image, he possesses a particular fondness for sweet things, with strawberry daifuku being his favorite food, which he appreciates partly because its name means good luck. His other hobbies include gardening and cooking.

His primary motivation throughout the story is to maintain his distance from the human world and others to prevent his curse from causing them harm. He views himself as unlucky and avoids forming close bonds, believing that any connection would only end in misery for the other person. In his role within the narrative, Hades is a student at the academy where gods are sent to learn about human love. His quiet nature makes him a more withdrawn participant, but his journey is central to the theme of overcoming personal tragedy. His relationship with the human heroine, Yui, is the catalyst for his development. Initially indifferent and cold towards her to keep her safe, he finds his resolve challenged by her persistent kindness and refusal to be scared away. A pivotal moment occurs when she makes him strawberry daifuku, a gesture that visibly touches him. Over time, Yui helps him see his curse from a new perspective, suggesting that his perception of misfortune is a matter of viewpoint. This insight allows Hades to begin considering that he might allow himself to enjoy life a little more, leading to him showing shy affection and even volunteering to play the prince in a school play to have a role that ends with him marrying Yui.

Hades's key relationships are shaped by his curse and his quiet nature. His bond with his nephew Apollon is one of deep care, though he finds Apollon's boundless energy difficult to manage at times. In contrast, his relationship with his brother Zeus is tense, as Zeus feels superior and does not treat Hades with the respect due to an elder brother. He shares a quieter, more supportive bond with Dionysus, often looking after him. As a member of the Astronomy Club, Hades displays a notable ability; he is very well-versed in constellations, though he tends to focus on the tragic myths behind the stars. His divine abilities are tied to his role as the god of the underworld, and while specific powers are not exhaustively detailed, his curse is an ever-present part of his identity. He is also known for his peculiar sense of humor, making puns that other gods find cold and lame. Outside of his own story, he is known to care for a pet tortoise named Sadalsuud, which fittingly means luckiest of lucky stars.