Kazuya Toujigamori, often called Toji by his friends and classmates, is a significant figure in the story as the initial love interest of the protagonist, Momo Adachi. He is a student at the same high school and was a friend of Momo's during their junior high years. Physically, Kazuya is depicted as somewhat tall with short, light-colored hair, most often shown as a light brown or gray in the anime, and brown eyes. His typical school attire consists of a standard uniform, including a white collared shirt, black pants, and brown shoes, which he sometimes complements with a blue sweater during colder seasons. He is also an athlete, with a notable dedication to baseball that was a primary focus for him during middle school.

In terms of personality, Kazuya is consistently portrayed as a kindhearted, thoughtful, and sincere individual who prioritizes the well-being of others, frequently placing their needs ahead of his own. His demeanor is generally quiet, serious, and stoic, although he becomes noticeably more open and outgoing when he is comfortable with someone. This sincerity is one of his defining traits, but it is also coupled with a significant level of naivety. Kazuya can be quite innocent and easily manipulated, as he often fails to recognize when others are taking advantage of his trusting nature. He tends to accept the first piece of information he hears without seeking further details, a flaw that makes him vulnerable to deception. This is further compounded by a certain obliviousness, particularly when it comes to understanding romantic situations and the hidden motives of those around him.

Within the narrative, Kazuya's primary role is central to the early romantic conflicts. He is the object of Momo Adachi's long-standing affection, a crush that began in junior high school. Their relationship forms a core part of the story's dramatic tension. The relationship between Kazuya and Momo is complex and evolves significantly. Initially, they rekindle their friendship from junior high, which eventually blossoms into a romantic relationship. However, this relationship is constantly challenged by misunderstandings, largely manufactured by another classmate, Sae Kashiwagi. Sae is also a key figure in Kazuya's life; he initially views her as a friend and confidant, unaware that she is actively scheming to steal him from Momo. His trust in Sae is a recurring point of vulnerability. In a particularly dramatic turn, Sae uses blackmail to force Kazuya into dating her, demonstrating how his desire to protect others can be exploited against him. His dynamic with Kairi Okayasu, another male classmate, is marked by rivalry, as Kairi also has feelings for Momo and often gets on Kazuya's nerves.

Throughout the story, Kazuya undergoes a notable character development arc. He starts as a somewhat passive and naive participant in the events around him, easily swayed by Sae's lies and unable to see the full truth of Momo's situation. As he gains more experience and the consequences of his naivety become clear, he learns to be more wary, particularly of Sae's manipulations. He becomes more active in his decisions, showing a willingness to sacrifice his own happiness for the sake of protecting Momo, such as when he agrees to Sae's blackmail demands. Later, he demonstrates growth by confronting Momo with a final choice about their future, showing a more decisive and mature side. His journey reflects a transition from a trusting boy to a more discerning young man who, while still kind, is capable of making painful choices for the greater good of the person he loves. As for notable abilities, Kazuya is primarily distinguished by his athletic skill, particularly as a dedicated baseball player. His physical prowess on the field is a notable part of his character background, though his most defining traits remain his personality and his central role in the story's love triangle.