Houx, also known in the human world as Shuuji Katou, is a wizard and the twin brother of another wizard named Saule. He shares a deep history with the protagonist, Chocolat Meilleure, as the two are childhood friends who grew up together in the Magical World. Houx and his brother serve as the guardians of the forest where the story's events begin, and their connection to Chocolat and her rival Vanilla Mieux dates back to their earliest days.

Physically, Houx is recognized by his light brown hair and matching brown eyes. He is typically seen wearing a green shirt with beige pants, and his most constant accessory is a white scarf lined with yellow. Bandages wrapped around his arms add a distinct element to his appearance. As a twin, he is the same height as his brother, which is approximately 165 centimeters.

In terms of personality, Houx is described as having a gentle and calm demeanor, which presents an interesting contrast to the more brash and argumentative side he shows, particularly when interacting with his brother. Like Saule, he can be impulsive and his straightforward nature can sometimes lead him into trouble, but his underlying character is one of kindness. This gentleness is particularly evident in his dedication to his hobbies, which include collecting medicinal herbs and practicing fortune-telling, specifically a special skill called the Bonfire Divination.

Houx's primary motivation stems from his deep affection for Chocolat. He and his brother argue frequently over who will become Chocolat's king should she succeed in becoming Queen of the Magical World. This personal longing drives him to take on a crucial role in the story when the girls travel to the Human World. To ensure Chocolat's safety during the Queen Selection exam, Houx and Saule follow her as her knights. In the human world, to remain close to her, they enroll in the same school and pose as Chocolat's cousins. In this setting, Houx presents himself as a protective figure, keeping a watchful eye over her interactions with others.

The dynamics of Houx's relationships are central to his character. His relationship with his twin brother, Saule, is competitive but close; they are rivals for the same girl's heart, yet they work together seamlessly as protectors. His relationship with Chocolat is one of unrequited love, and he becomes visibly jealous and angry when rival suitors like the mysterious Pierre get too close to her. This possessiveness is rooted in a genuine, albeit unreturned, romantic feeling. He also harbors a deep-seated insecurity about losing Chocolat to Pierre, which surfaces in moments of tension between the two male characters, even leading to a physical fight over her. Although Houx initially shows little interest in Vanilla Mieux, his feelings shift significantly by the end of the story. While one of his main rivals, Waffle, shows interest in him, Houx does not return these affections and often tries to avoid her. Instead, the narrative concludes with Houx developing feelings for Vanilla, ultimately marrying her.

Throughout the series, Houx undergoes notable development in his emotional maturity. He begins as a boy fervently fighting for the attention of his childhood crush but grows to accept a different future. His shift in affection from Chocolat to Vanilla represents a significant evolution from his initial, more simplistic childhood crush to a more mature adult relationship.

As a wizard, Houx possesses specific magical abilities. He is particularly proficient in the Bonfire Divination, a form of fortune-telling using a campfire that allows him to foresee the arrival of specific people. He can also use magical attacks in combat, wielding an ivy-based weapon called Ruban de Lierre. He and his brother utilize these vine-like whips or swords in battle, most notably when they confront powerful enemies to protect the queen candidates.