Endou Mamoru is the central protagonist of the original Inazuma Eleven storyline, a passionate and determined student at Raimon Junior High School who serves as the goalkeeper and captain of the school's football club. His journey into the sport began in childhood when he discovered a storage room filled with his grandfather's belongings. Endou Daisuke, a legendary goalkeeper, left behind notebooks full of techniques that would inspire young Endou to pursue football with all his heart. Despite his mother's initial objections, as she associated the sport with her father's supposed death, Endou's persistence eventually won her support. This family connection remains a powerful force in his life, as he holds great admiration for his grandfather and diligently studies the technique-filled notebooks Daisuke left behind.

Personality defines Endou more than any other attribute. He is described as a cheerful, soccer-loving individual who never gives up and consistently puts the wellbeing of others before his own. His natural, upbeat, and positive personality has a magnetic quality, attracting both allies and rivals to his side. People often call him a soccer freak due to his overwhelming love for the game, but his teammates benefit greatly from his mental strength and encouragement. Even when facing seemingly impossible disadvantages, Endou finds ways to lead his team toward victory. He trains harder than anyone else, driven by a genuine desire to face even stronger opponents rather than a simple need to win. When he does lose, he shows no disappointment in defeat, instead striving to improve for the next match. This unshakable spirit is occasionally tinged with overconfidence in his grandfather's ultimate techniques, but he learns and adapts when those techniques are overcome.

Endou's primary motivation is to enjoy football and share that joy with others. His love for the sport is so profound that a coach once noted the best compliment for him would be to call him the biggest soccer freak in the world. This passion drives him to recruit new members for his team, push through devastating losses, and never abandon his dream of building a strong football club. His role in the story begins with Raimon's football club on the verge of disbandment due to insufficient members. Through sheer determination and his infectious enthusiasm, Endou gathers the players needed to form a full team, eventually leading Raimon to the Football Frontier tournament and beyond. He later becomes the captain and main goalkeeper for Inazuma Japan in the international FFI tournament.

Key relationships shape Endou's journey significantly. His best friends include Gouenji Shuuya, the powerful forward whose arrival allows Raimon to survive its first真正的 challenge; Kidou Yuuto, the brilliant strategist who joins from Teikoku Academy; and other trusted teammates such as Kazemaru Ichirouta and Kabeyama Heigorou. His bond with his grandfather Daisuke, though posthumous in much of the story, guides his development as a goalkeeper. In the original series, his emotional intelligence allows him to detect when teammates are struggling, as seen when he realizes his own intensity had pushed Kazemaru into a dark place. He shows great care for others, such as staying in a hospital with a childhood friend who had lost her memories. In the anime continuity, Endou eventually marries Natsumi Raimon, the chairman's daughter, and grows more mature and calm as an adult.

Character development transforms Endou notably across the timeline. In the original series, as a thirteen or fourteen year old, he is hyperactive, loud, and endlessly talkative about football. After a particularly challenging battle against Aliea Academy, his personality tempers as he realizes the importance of his teammates over his own ambition. He learns that pushing everyone too hard can have consequences, such as when his relentless drive contributed to a teammate's emotional crisis. Ten years later in the Inazuma Eleven GO series, Endou appears as a twenty four year old who has matured considerably. He becomes the coach of a new Raimon team, displaying a much calmer, smarter, and more strategic demeanor. While his love for football remains as passionate as ever, he no longer overacts or talks endlessly. He knows when to speak and when to remain silent, showing a newfound maturity that serves him well as a mentor. As a coach, he is kind and caring toward his players, using motivational encouragement to help them overcome their limitations.

Endou possesses remarkable abilities as a goalkeeper and occasionally as a libero, an attacking defender role he assumes in the second season. His signature technique is God Hand, which he learns from his grandfather's notebook, summoning a giant ethereal hand to block incoming shots. This technique later evolves into True God Hand. Other notable defensive techniques include Majin the Hand, where he conjures a demon-like entity to perform a powerful palm strike; Ijigen the Hand, which creates a spiraling force field that redirects the ball away from goal; and God Catch, the final technique left behind by his grandfather. For offensive situations or counterattacks, he uses moves like Fist of Justice, a giant glowing punch, and Megaton Head, a similar technique using his head. He also participates in combination techniques with teammates, including Inazuma Break with Gouenji and Kidou, The Earth with Gouenji and Fubuki Shirou, and Tri Pegasus with Ichinose and Domon. His abilities grow throughout the series as he faces increasingly powerful opponents, always striving to improve and protect his team's goal.