Ginji Kurokawa is a student in Class 3-D of Shirokin Gakuen, the same delinquent-heavy homeroom class as the protagonist Kumiko Yamaguchi. His background is grounded in a working-class neighborhood; he is often seen as a rough-and-tumble local who has grown up on the streets, which contributes to his street-smart nature and his tendency to rely on physical solutions to problems.

In terms of personality, Ginji is hot-headed, impulsive, and notably more aggressive than his best friend, Shin Sawada. He has a short temper and is quick to resort to his fists when provoked, often serving as the initial spark for the class’s conflicts. Despite his belligerent exterior, he possesses a strong sense of loyalty and a hidden soft spot for his friends and teacher. He can be surprisingly earnest and straightforward, lacking the cynicism that some of his peers display, which makes him one of the more emotionally transparent members of the group. His motivations are primarily driven by loyalty and a desire for respect. He seeks to prove his strength not out of malice, but to protect his own and to maintain the honor of his class. Initially dismissive of Yankumi, he becomes highly motivated to protect her once he recognizes her genuine care for them, seeing her as someone worth fighting for.

Within the story's framework, Ginji acts as both a catalyst for conflict and a representation of the school's rough environment. He is frequently involved in brawls with rival schools or yakuza members, forcing the class into dangerous situations from which they must then extricate themselves. His role is often that of the muscle and the emotional core of the student group, providing a contrast to the cooler, more calculating Shin. His key relationships are primarily with Shin Sawada, whom he respects and follows as a leader, and with Kumiko Yamaguchi, also known as Yankumi. The dynamic with Shin is one of long-standing brotherhood, where Ginji acts on instinct while Shin provides strategic guidance. With Yankumi, his relationship evolves from antagonistic annoyance to fierce protectiveness and familial affection, often being one of the first to leap to her defense.

Ginji’s development throughout the narrative is gradual but clear. He begins as a stereotypical delinquent who trusts only brute force, but he learns to temper his aggression with trust and strategy, largely due to Shin and Yankumi’s influence. He moves from seeing teachers as enemies to seeing Yankumi as a true mentor and mother figure, which softens his rougher edges without diminishing his fighting spirit. Notable abilities include exceptional physical strength and endurance, making him a formidable fighter in street brawls. He is proficient in basic combat techniques learned from years of fighting, though he lacks any formal training. His greatest asset is his unwavering courage and his willingness to take a hit for his friends, which often turns the tide of a fight by sheer force of will.