Ahiru no Ah-kun, often shortened to simply Ah-kun, is a character from the anime Moetan who originates from a magical kingdom. His full name is Arcs Sheldart El Vias, and his true form is that of a young and handsome man with long blond hair. However, due to circumstances in his past, he has been banished to the human world and is trapped in the form of a small, talking duck, often wearing a hat and a tie. The reason for his exile is a scandal involving his inappropriate behavior. He is a self-admitted pervert with a strong lolicon fetish, and he was originally banished for peeping on young girls. The situation was complicated by Alice Shiratori, a magical girl who framed him as a peeping tom after he rejected her romantic advances, claiming he could not fall in love with her due to her large chest.

Personality-wise, Ah-kun is utterly shameless and serves as the primary source of comic relief in the story. He makes no effort to hide his perverse nature, often making lecherous remarks and becoming visibly excited in inappropriate situations. His most notable recurring behavior is his reaction to the main character, Ink Nijihara, transforming into her magical girl form, Pastel Ink. During the transformation sequence, Ink is briefly naked, and Ah-kun is shown to be completely entranced, often drooling profusely or suffering a nosebleed, which is a common anime trope for strong sexual arousal. He is frequently seen running into a scene, making a lecherous comment, and then fleeing just before a police officer arrives looking for a suspicious person.

Ah-kun's primary role in the story is that of a mentor and enabler. He is the one who grants Ink the power to transform into a magical girl, providing her with a magical flip phone to perform her "Magical Change". He explains that her mission is to help people, and more specifically, he encourages her to use her new alter ego to tutor her crush, Nao-kun, in English. Despite his lack of morality, his motivation is tied to his banishment; he needs Ink to act as a magical girl in the human world, likely as a form of redemption or simply to fulfill the duties he can no longer perform himself. His relationship with Ink is built on a strange, comedic partnership. While she relies on him for her powers, she is also frequently embarrassed and exasperated by his perverted antics. A significant part of his background involves his antagonistic relationship with Alice Shiratori, whose false accusations led to his current predicament. Over the course of the series, there is a development where his innocence regarding the peeping tom accusation is revealed, adding a layer of tragic irony to his lecherous persona, as he was punished for a crime he did not commit while remaining genuinely perverted in other ways. As a magician, his notable abilities include the knowledge of magical arts, the power to bestow magical girl abilities onto others, and the capacity to transform between his human and duck forms, although he is confined to the duck form while on Earth.