Kazuya Tojigamori, known to nearly everyone as Toji, is a central character who serves as the initial love interest for the protagonist Momo Adachi. He is a student at the same high school as Momo, and their history stretches back to their days in junior high, where they developed a close friendship. During that time, Toji was intensely focused on baseball, which remains a significant part of his identity throughout the story.

Physically, Toji is depicted as somewhat tall with short, light hair, which is most often shown as a light brown or gray in the anime adaptation, and brown eyes. His typical attire is his school uniform, consisting of a white collared shirt, black pants, and brown shoes, sometimes complemented by a blue sweater in colder weather.

Toji's personality is defined by a genuinely kind and thoughtful nature. He is a quiet and serious individual who becomes noticeably more outgoing when he is around people he trusts and feels comfortable with. His primary motivation is a deep-seated desire to help others, often placing their needs and well-being above his own. This selfless devotion, particularly toward Momo, drives many of his actions throughout the series. However, his good nature is coupled with a notable naivete. Toji can be quite dense when it comes to understanding romantic situations and the hidden motives of others, which makes him slow to recognize not only Momo's feelings for him but also the malicious scheming of those around him. He tends to be hard-headed and often accepts the first piece of information he receives without questioning its validity.

In the story, Toji's role is largely defined by his romantic relationship with Momo Adachi, who has harbored a crush on him for years. Their friendship eventually blossoms into a relationship, but it is constantly tested by external forces. A pivotal part of his journey involves his fraught relationship with Sae Kashiwagi. Initially, Toji views Sae as a close friend and confidant, unaware that she is secretly working to sabotage Momo's happiness out of jealousy. Sae frequently manipulates Toji's trusting and straightforward personality, feeding him lies about Momo and later even blackmailing him into ending his relationship with Momo and dating her instead. This experience is a key part of his development, as the repeated betrayals and misunderstandings force him to become less naive and more perceptive of people's true natures. Over time, he learns to be wary of Sae's manipulations and grows more capable of protecting his relationship with Momo.

Toji's relationship with the other male lead, Kairi Okayasu, is initially one of rivalry and annoyance. Kairi's flamboyant and persistent personality grates on the more reserved Toji, especially when it comes to his feelings for Momo. Despite their rivalry, Toji's inherent goodness never fades. Even when his own heart is broken, his greatest wish remains Momo's happiness, demonstrating a deep, unselfish love that allows him to step aside when he believes it is the right thing to do. Regarding his abilities, Toji is a talented baseball player, a fact that he was especially dedicated to during middle school. His athleticism is a notable aspect of his character, though his most significant "ability" is perhaps his unwavering loyalty and emotional resilience.