Free Underbar is a central character in the anime Fairy Gone, serving as the Deputy Captain of the First Unit of Dorothea, a government agency responsible for regulating and investigating crimes involving fairies in the postwar era. He is a man of average to tall stature with short, dark brown hair and sharp blue eyes, often accompanied by a small, faded beard that adds to his serious appearance. His typical attire reflects his role as an officer, favoring practical and professional clothing suitable for field operations.

Free's personality is defined by a distinct contrast between his stern exterior and a deeply caring nature. He is a serious, no-nonsense individual who approaches his duties with a high level of professionalism and discipline. This can make him appear cold or strict at first glance. However, beneath this tough facade lies a compassionate and protective man who genuinely cares for his subordinates and colleagues. He is known for being level-headed and strategic, rarely acting on impulse and always considering the well-being of his team. This combination of leadership and empathy has earned him a great deal of respect and trust within the Dorothea organization.

Free's background is rooted in the devastating Unification War, where he fought as a fairy soldier for the nation of Ledrad. During this time, he was known as a formidable warrior, wielding two swords in combat alongside his fairy. The war shaped his worldview and left him with a strong sense of duty to protect the peace that was finally established. After the conflict, he transitioned into Dorothea, using his combat experience to serve as a peacekeeper. One of his key motivations is to atone for the past and prevent the horrors of war from repeating, which drives him to pursue justice rather than personal revenge. He is also driven by a personal mission to find his former comrade, Wolfran Row, whose path took a dark turn after the war.

In the story, Free plays a pivotal role as a mentor and partner to the protagonist, Marlya Noel. He first encounters her during an undercover operation with the Gui Carlin mafia, where she becomes accidentally possessed by a fairy. Seeing her potential and the danger she is in, he offers her a choice: be arrested or join Dorothea. She chooses to join, and Free becomes her direct superior and most trusted partner. His relationship with Marlya is central to the narrative; he guides her through the complexities of her new role, helps her control her powers, and provides crucial emotional support as she searches for her childhood friend, Veronica. Their bond develops into a strong, professional friendship built on mutual trust and respect.

Another key relationship is with Wolfran Row, his former brother-in-arms from the war. Their friendship is shattered by the trauma of the conflict, which led to the loss of Wolfran's family and his subsequent turn to terrorism. Much of Free's personal arc involves confronting Wolfran, not out of a desire for revenge, but from a wish to understand his fall from grace and potentially stop him from causing further harm. In their final confrontation, Free defeats Wolfran but refuses his old friend's request to be killed, symbolizing a rejection of the cycle of violence and a commitment to a different future.

Free's development throughout the series sees him grappling with his identity as a former weapon of war and his new purpose as a protector. He learns to balance his rigid adherence to rules with the understanding that some situations require compassion and flexibility, a lesson he often learns from Marlya. He moves from being a soldier haunted by his past to a leader who actively shapes a more peaceful future, openly affirming his place within Dorothea as a shield for the innocent.

As a fighter, Free is exceptionally skilled. He is a master swordsman who primarily fights with two longswords, a style that grants him both offensive power and defensive dexterity. His physical abilities are superhuman, allowing him to dodge bullets and fight against other enhanced fairy soldiers. His true power, however, comes from his symbiotic fairy, Red Hood. Red Hood manifests as a massive, bipedal, wolf-like humanoid known for its ferocity in close combat, using its powerful claws to tear through enemies. For ranged attacks, Red Hood can unleash devastating sonic waves from its mouth that are capable of destroying walls and other large structures. Free is a strategic fighter who often engages enemies with his swords first, only summoning Red Hood when the situation becomes dire. This synergy between his precise swordsmanship and Red Hood's brutal, brute-force style makes him one of the most formidable agents in Dorothea. A key weakness linked to this ability is that any damage inflicted upon Red Hood is also suffered by Free, creating a direct physical link between them.