Kazuya Tojigamori, commonly known as Toji, is a high school student and one of the central figures in the romantic dynamics of his social circle. He has a somewhat tall build, with short, light hair that is depicted as light brown in manga illustrations and gray in the anime adaptation, paired with brown eyes. His standard attire is his school uniform, which consists of a white collared shirt, black pants, and brown shoes, supplemented by a blue long-sleeved sweater during colder months.

Toji is generally a quiet and serious individual, though he becomes noticeably more outgoing and relaxed when in the company of people he trusts. His core personality is defined by a kindhearted and thoughtful nature, with a strong desire to help others that often leads him to prioritize their needs above his own. This selflessness is a defining trait, but it is coupled with a significant degree of naivete. He is often unaware when others are taking advantage of his good nature and tends to believe the first thing he hears without seeking further information, making him surprisingly easy to deceive. This innocence and straightforwardness, while sincere, contribute to many of the misunderstandings that arise around him. He is also an athletic individual, having been a baseball player during middle school and continuing to be involved in sports.

Toji's primary motivation throughout the story is his deep-seated care for Momo Adachi, whom he has known since junior high school. He is her initial love interest, and his actions are consistently driven by a desire to protect her and ensure her happiness, even when it requires significant personal sacrifice. His role in the narrative is that of the earnest and reliable first love, a figure whose quiet devotion is contrasted with the more dynamic and forward nature of his rival. He becomes a pawn in the schemes of Sae Kashiwagi, but eventually gains more agency as the plot progresses. Despite being the object of Momo's long-standing crush, he is initially clueless about her feelings for him.

His key relationships define much of his journey. The most important is with Momo Adachi, his friend from junior high who becomes his girlfriend. Their relationship is tested repeatedly due to external interference and their own lack of trust early on, but they share a genuine love for one another. Toji's interactions with Sae Kashiwagi are profoundly complex. She begins as a classmate and close friend whom he uses as a confidant. After he learns of her manipulative and cruel treatment of Momo, they grow distant, only for Sae to later blackmail him into dating her, a period during which he never develops true feelings for her. His relationship with Kairi Okayasu is one of rivalry, as they compete for Momo's affections. Toji finds Kairi's demeanor irritating, but over time, he is forced to rely on Kairi's help to protect Momo from Sae, leading to a grudging respect between the two.

Throughout the series, Toji undergoes significant development. He starts as a passive and easily misled character, but experience teaches him to be wary of Sae's manipulations. He evolves into someone who actively makes difficult decisions to protect Momo, such as breaking up with her under duress and later encouraging her to be with Kairi when he believes it is best for her. His journey culminates in him demanding that Momo make a final decision between him and Kairi, ultimately accepting her choice to be with the other boy and prioritizing her happiness over his own desires. His notable ability lies not in a special skill, but in his resilience and emotional strength. He is a reliable and devoted figure, capable of great sacrifice, who endures heartbreak while remaining a supportive presence in Momo's life. He is often described as a solid, trustworthy person, even if he is slow to understand the true nature of those around him.