Ginta Toramizu is the main protagonist of the story, a fourteen-year-old student living in Tokyo, Japan. As a child, Ginta was often told stories of the fairy-tale land of MÄR-Heaven by his father, Danna, despite his mother's protests. His father suddenly disappeared without a trace when Ginta was eight years old, leaving his mother to write fairy tales to support the family. On Earth, Ginta was a near-sighted, video game loving underachiever who frequently fell asleep in class, a habit for which he was often picked on by classmates and teachers. His only close friend was a girl named Koyuki, on whom he harbored a secret crush. Ginta constantly dreamed of a fantasy world where he was a hero, and he often told Koyuki about these dreams, as she was the only person who believed they were real.

Ginta is a fun-loving and carefree boy, recognizable by his long, spiky blonde hair typically tied into a ponytail. He possesses a very loyal personality and is driven to fight to protect those who need help, preferring to avoid killing his opponents if possible. Despite his initial weaknesses on Earth, Ginta is immensely determined and grows to become a courageous individual who refuses to give up, even when faced with seemingly unwinnable battles. A defining trait is his passionate and sometimes reckless nature, which is tempered by his strong sense of justice and his role as the emotional core of his group, keeping his team together through difficult times.

His motivations are deeply personal. Initially, he is simply excited to be in the world he has always dreamed of, but he quickly learns that he was summoned by a boy named Alviss for a specific purpose: to save MÄR-Heaven from the evil Chess Pieces that are trying to conquer it. During his journey, he also seeks to uncover the mystery of his father's disappearance, which is directly tied to the fate of this other world. His role in the story is that of the central hero and the captain of Team MÄR, which he forms to compete in the War Games, a tournament against the Chess Pieces that will decide the future of MÄR-Heaven. Throughout the War Games, Ginta serves as Team MÄR's primary fighter, facing off against many of the Chess Pieces' most powerful members.

Key relationships define Ginta's journey. His most important partner is Babbo, a legendary, sentient weapon known as an ÄRM that resembles a kendama and possesses its own distinct, often annoying, personality. Despite their bickering, they form a deep bond. He also forms close friendships with Jack, a young farmer who is his first friend in MÄR-Heaven; the powerful witch Dorothy, who has a noticeable crush on him; and the mysterious Alviss, who initially doubts Ginta's abilities but comes to respect him. His dynamic with Princess Snow is significant, as she is the counterpart in MÄR-Heaven to his love interest on Earth, Koyuki, leading to a complicated romantic subplot. His primary antagonist is Phantom, the leader of the Chess Knights, with whom Ginta develops a personal rivalry.

Throughout the series, Ginta undergoes significant development. He begins as an underdog, a self-proclaimed loser who is physically weak and an academic failure on Earth. Upon arriving in MÄR-Heaven, where gravity is lower, he gains superior physical strength, incredible stamina, and perfect eyesight, but his growth is not just physical. He starts with no knowledge of ÄRMs and is an unskilled but strong brawler. Through intense training inside a magical dimension called the Training Gate, which compresses months of training into days, and through his many battles, he matures into a strategic and powerful warrior capable of unlocking Babbo's full potential. He evolves from a dreamer into a true hero, earning the respect of his allies and even some of his enemies.

Ginta's notable abilities stem from the unique properties of MÄR-Heaven, which grant him superhuman levels of strength, speed, and endurance far beyond that of a normal human boy his age. His primary tool is his ÄRM, Babbo. Babbo is no ordinary weapon; it has a mind of its own and can change its shape and size at Ginta's command, transforming into various forms such as a hammer or a sword. Ginta learns to use Babbo's special attacks, most notably the Gargoyle, a powerful transformation that grants him armored wings for enhanced combat, and Alice, a holy form that can counteract dark magic and heal. As the series progresses, he learns to master these forms, using his quick thinking and Babbo's unique abilities to overcome opponents who are often much more experienced than him.