Ginta Suō is a central character known for being the childhood friend and former crush of the protagonist, Miki Koishikawa. He is a student at Toryo High School and an active member of the school's tennis team, where he is considered the ace of his grade. Ginta has brown hair and brown eyes, and he stands at approximately 182 centimeters tall.

In terms of personality, Ginta is energetic, enthusiastic, and impulsive, often acting on his passions before thinking them through. He tries to present a cool and tough exterior, but underneath this surface he is quite sensitive, vergonzoso (easily embarrassed or shy), and sometimes lacks self-confidence. He can become silly and emotional when excited, and he is known to get flustered when provoked by his friends or by Yuu Matsuura. Despite his outward bravado, he is a single-minded and straightforward person who values honesty and dislikes lies and deception.

Ginta's history is deeply intertwined with Miki Koishikawa. During junior high school, Miki had a significant crush on him and confessed her feelings in a note. The note was intercepted and read by his classmates, and in an effort to downplay the situation due to embarrassment, Ginta denied having any interest in her. Unfortunately, Miki was watching this scene unfold, leading to a painful misunderstanding that drove a wedge between them for some time, even though he secretly shared her feelings. They eventually reconciled and became close friends again, but the unresolved romantic tension remained.

Ginta's primary motivation in the story is navigating his complicated feelings for Miki, which are reignited when Yuu Matsuura enters the picture as his new rival. The arrival of Yuu makes Ginta realize that he still has strong feelings for Miki. This leads him to enter into a scheme with Arimi Suzuki, Yuu's ex-girlfriend. The two agree to pretend to be a couple with the goal of making Miki and Yuu jealous and potentially breaking them apart. However, this plan backfires in an unexpected way. Through the process of spending time together as a fake couple, Ginta begins to develop genuine romantic feelings for Arimi, and she eventually reciprocates them. This transition marks a significant turning point for his character, moving him from a rival in a love triangle to the protagonist of his own romance.

His key relationships define his role in the story. His friendship and history with Miki Koishikawa are the foundation of his initial involvement in the plot. He shares a competitive and tense dynamic with Yuu Matsuura, whom he views as a rival both in tennis and in love. His relationship with Arimi Suzuki evolves from a strategic alliance into a sincere and loving partnership. He also has a cousin, Tsutomu Rokutanda, who is hopelessly in love with Arimi. This creates a source of familial tension and rivalry, as they often clash over her, though their relationship is also marked by childish and competitive bouts.

Throughout the series, Ginta shows significant development. He begins as a boy unable to properly express his feelings, leading to a missed opportunity with Miki. He matures as he learns to move past his first love and opens his heart to someone new. By the end of the story, he has formed a committed relationship with Arimi. In the sequel series, Marmalade Boy Little, Ginta and Arimi are married. Their marriage faces challenges due to frequent separations caused by their respective careers, leading them to consider divorce. However, they ultimately recommit to each other and decide to start a family, later having a son named Haruta. In terms of abilities, Ginta is notably a highly skilled tennis player, recognized as the ace of his school's team, and he serves as a capable rival to Yuu on the court.