Kazuya Toujigamori, commonly referred to as Toji, is a central figure who develops from a childhood friend and initial love interest to a more complex individual whose primary concern is the happiness of others. His background is rooted in middle school, where he was a dedicated baseball player and formed a close friendship with Momo Adachi, a connection that carries into their high school years. Toji is physically characterized as somewhat tall with short, light hair, typically depicted as light brown or gray in the anime, and brown eyes. He is most often seen in his school uniform, which includes a white collared shirt and black pants, sometimes with a blue sweater in colder weather.

Toji's personality is defined by a quiet, sincere, and kindhearted nature, often putting the needs of others before his own. He is generally serious, though he becomes more outgoing around people he is comfortable with. His athletic background, particularly in baseball, contributes to his reputation as a serious and reliable individual who is respected by his teammates. However, this earnestness is accompanied by a notable naivety; he can be surprisingly slow to grasp romantic subtleties and is often unaware when others take advantage of his goodwill. This makes him easily manipulated by those who exploit his trusting nature, as he tends to believe the first thing he hears rather than seeking further information.

His primary motivation throughout the story revolves around protecting those he cares about, especially Momo. Toji's role in the narrative is largely defined by the complex web of relationships and misunderstandings created by the antagonist, Sae Kashiwagi. Initially unaware of Sae's manipulative personality, he becomes a pawn in her schemes to sabotage Momo. He and Momo eventually begin dating, but their early relationship is plagued by a lack of trust, causing them to argue when Sae spreads lies. Toji's deep-seated feelings for Momo cause him to choose to be with her after a series of reconciliations. The depth of his devotion is most clearly shown when Sae blackmails him into ending his relationship with Momo and dating her instead. Toji agrees to this solely to protect Momo from the threat Sae holds over her, an act of self-sacrifice that defines his character. After Sae tires of him, he steps aside when Momo becomes involved with Kairi Okayasu, his rival for her affections.

Key relationships are central to Toji's development. His relationship with Momo evolves from a friendship and initial crush, to a boyfriend, and eventually to a deep, selfless love where his greatest wish is for her happiness, even if it is not with him. His dynamic with Sae is one of manipulation and betrayal; after being her close friend and confidant, he grows distant upon realizing her true nature, only to be forced into a relationship with her through blackmail. In the sequel series Peach Girl Next, they are roommates, indicating a complex, though not romantic, reconciliation. His rivalry with Kairi is intense, as Kairi's flirtatious and disruptive personality stands in stark contrast to Toji's more serious and reserved demeanor. Despite their mutual annoyance, Toji is forced to rely on Kairi's help to rescue Momo from Sae's plots, leading to a grudging respect between them.

Throughout the series, Toji shows significant development. He begins as a somewhat passive and easily fooled individual but learns from his experiences, becoming more wary of deception. His character arc leads him to take a more active role in the plot, culminating in him forcing Momo to make a final decision between him and Kairi, demonstrating his maturity and his ultimate desire for her genuine happiness. While he does not possess any special abilities, his notable traits are his athleticism as a baseball player and his quiet integrity, which make him a solid and reliable presence.