Nishikata is a middle school student seated next to Takagi in class. He possesses black hair, small black pupils, and a fair complexion. During his school years, he wears a white button-down shirt over a plain white-green t-shirt, paired with navy blue pants and white school shoes featuring red soles. As an adult, his hair becomes shorter and neater, and his physique turns noticeably muscular from his profession as a physical education teacher and consistent fitness routine. His adult wardrobe often consists of casual attire like t-shirts and sweatpants.

Easily embarrassed, particularly by Takagi's teasing, Nishikata reacts with visible blushing and agitation. Despite consistent failures, he remains determined to outwit her and tease her back, planning strategies days in advance, a drive that sometimes distracts him from schoolwork. He strictly adheres to self-imposed punishments, like performing ten push-ups for each teasing incident, showcasing perseverance and discipline. Alongside this competitiveness, he exhibits kindness and patience, especially toward children, a trait that carries into his teaching career. He is moralistic and avoids actions that might hurt or insult others.

Nishikata harbors a crush on Takagi but struggles to acknowledge his feelings, often misinterpreting their interactions as rivalry. He becomes flustered during romantic situations, such as when Takagi references relationships or when they share moments like holding hands or walking home together. He actively protects Takagi's well-being, shielding her from dangers like falling objects, though she sometimes misinterprets these acts. He notices subtle changes in her emotions, like refraining from teasing due to distress, and responds with supportive gestures, such as comforting her during family disappointments.

In adulthood, Nishikata marries Takagi, and they have a daughter named Chi. His personality matures; he becomes more confident and responsible yet remains easily flustered when teased by Takagi in front of Chi. As a physical education teacher, he earns student respect for his athleticism. He shares a close bond with Chi, engaging in playful activities or teaming up to tease Takagi, though their plans usually fail. He expresses deep affection for his family, becoming emotional over milestones like Chi's childhood crushes. His protectiveness extends to parenting, balancing affection with occasional strictness.

Unbeknownst to them, Nishikata and Takagi interacted as children through an arcade game, competing for high scores under usernames without recognizing each other. Their formal meeting occurred on the first day of middle school when Nishikata found Takagi's lost handkerchief, returned it to the lost-and-found, and arrived late to class. Seated beside her, Takagi teased him about his tardiness, initiating their daily dynamic blending rivalry with mutual care.