Allen Schezar is a central figure in the story, introduced as a charismatic and exceptionally skilled knight from the kingdom of Asturia. He is a member of the Knight Caeli, an elite order of swordsmen, and also serves as the pilot of a Guymelef named Scherezade.

On the surface, Allen is the picture of composure and chivalry. He is friendly, easygoing, and confident, often appearing as the perfect gentleman. He has a well-known reputation as a ladies' man, treating women with politeness and charm, which is a natural part of his courteous demeanor. However, this calm and noble exterior conceals a more tormented interior. Allen is a person who internalizes his suffering, and his past is marked by profound loss and grief. He is mature and prefers to think before acting, serving as a stark contrast to the more impetuous and inexperienced prince, Van Fanel.

Allen's motivations are deeply rooted in the tragedies of his past. When he was younger, his younger sister, Celena, was abducted by the mysterious empire of Zaibach. His father, Leon, subsequently vanished while searching for the secrets of Atlantis, and his mother died of a broken heart soon after. These events left Allen alone and fueled a deep resentment toward his father, whom he blames for abandoning the family in pursuit of a dangerous obsession. This unresolved pain and his desire to find his sister are powerful forces that drive many of his actions.

Within the story, Allen occupies a multifaceted role. He is initially a helpful ally to the protagonists, Hitomi and Van, and acts as a foil to Van, highlighting the young king's inexperience with his own worldly wisdom and skill. His personal history also creates complex entanglements. He had a secret romance with Princess Marlene of Asturia, which resulted in the birth of a son, Prince Chid, a fact that the prince remains unaware of. He has also captured the heart of another princess, Millerna, who is in love with him. Later in the series, his feelings for Hitomi Kanzaki become a significant plot point, and he becomes romantically involved with her, even proposing, largely due to the machinations of the series' antagonist, Dornkirk. His protective nature toward Hitomi is partly explained by her resemblance to his lost sister.

Throughout the story, Allen shows notable development, particularly in how he confronts his past. He begins as a man haunted by his family's disappearance, carrying a heavy burden of grief and anger. His interactions with Hitomi and Van, as well as the eventual revelations about his father's fate, force him to re-evaluate his past and his motivations. He must also contend with his own possessive and jealous tendencies, which emerge as he grows closer to Hitomi and sees her bond with Van strengthening.

In terms of abilities, Allen is one of the most formidable fighters in the world of Gaea. He showed exceptional swordsmanship from a young age and further honed his skills by training under Balgus of Fanelia, one of the three master swordsmen on the planet. This training transformed him into a knight of immense prowess, making him a powerful ally and a dangerous opponent. In addition to his skill with a blade, he is a highly proficient pilot of his Guymelef, the Scherezade, demonstrating tactical acumen and combat experience in battle that surpasses that of Van at the start of their journey.