Aransil is a prominent character in the anime, known as the retired hero and the biological father of the protagonist, Dariel. His background is steeped in tragedy and heroism. In his youth, he was a legendary figure celebrated for his immense power, particularly his rare ability to master all four types of aura, a talent he would later pass down to his son. His peaceful life ended thirty years before the main story when his wife was killed during an attack by the demon Beseria, and his infant son disappeared. This loss filled him with a deep and burning hatred for the demon race, transforming him into a fierce and merciless warrior against them. He eventually retired from his role as hero after being injured in a battle with the powerful demon Granbaza, passing the title to a young woman named Lady.

Aransil's personality is a study in contrasts, shaped by his past. On the battlefield, he is known for being a cold, ruthless, and seemingly heartless fighter. However, this exterior masks his true nature, which is gentle, kind, and easygoing, especially around children. He enjoys playful moments and is known to be friendly with villagers, even signing autographs, revealing a warm and social side. This softer personality emerges more fully as the story progresses and he reconnects with his lost family.

Aransil's primary motivation for much of his life has been vengeance against demons, a drive fueled by the death of his wife and the loss of his son. This hatred causes him to attack demons on sight without hesitation. However, his role in the story is to reunite with his son and discover the family he thought he had lost. His motivations shift from pure vengeance to a desire to protect his newfound family, culminating in a realization that he can fight not just from hatred, but with the heart of a true hero. He is not a main character who drives the plot of every episode, but his presence is a key catalyst for major events and character development, particularly for Dariel.

Aransil's relationships are central to his character. His most significant relationship is with his son, Dariel. For most of his life, Aransil believed his son was dead, and Dariel himself grew up unaware of his true father, having been adopted and raised by the demon Granbaza. Their reunion is fraught with misunderstanding, as Dariel initially only knows Aransil's cold, battle-hardened reputation, leading to a tense confrontation. However, this eventually leads to reconciliation and gratitude for the life Dariel was given. His relationship with Granbaza, his former enemy and Dariel's adoptive father, is a complex rivalry that transforms into mutual respect. They eventually put aside their deep-seated hatred to fight side-by-side against a common threat, an event that helps Aransil find a new sense of purpose. Upon discovering that he has a grandson, Gran, Aransil becomes an excessively doting and proud grandfather, openly showing a love and passion for his family that was hidden for years.

Throughout the anime, Aransil undergoes notable development. He begins as a figure haunted by a tragic past and driven by a consuming hatred for an entire race. A key turning point occurs when he is forced to confront his old enemy Granbaza in his son's village, an event that ends without violence but forces him to begin reconciling with his past. His development culminates in the final battle, where he realizes he is fighting to protect rather than simply for revenge, remarking that it is the first time he feels like a true hero. This journey transforms him from a bitter, vengeful warrior into a loving father and grandfather who has found peace.

In terms of abilities, Aransil is exceptionally powerful. He is famous for his rare talent in all four branches of aura, which allows him to perform a wide array of powerful techniques. This skill was the source of his legendary status as the hero and a rival to the strongest of demons. Even in his retired and older age, with his power somewhat diminished, his strength still surpasses that of the current hero, Lady. In combat, he wields a long staff, which he can envelop with different types of aura to execute cutting attacks and other martial techniques.