Aster

Face and Hairstyle: He has tousled, voluminous, sky-blue (turquoise) hair with a couple of contrasting white strands near his face. His skin is tan.
Accessories: He wears round, thin-framed glasses. The lenses often glare or reflect light, giving him a simultaneously intelligent and slightly mysterious look.
Clothing style: Aster dresses like a typical young scholar, bookworm, or graduate student. His look is complemented by an academic or student wardrobe: vests, collared shirts, and blue-violet elements, emphasizing his magical specialization.
Build: He's rather thin and lanky, accentuating the hunched posture of a perpetual librarian who spends hours poring over tomes. Astaire's character, personality, and communication style from "Fantasy Patrol" very accurately reflect the classic trope of the cunning villain in the mask of a "harmless nerd."

Duplicity and deception: Behind the facade of a modest, quiet, and helpful bookworm lies an incredibly ambitious, calculating, and selfish manipulator. He masterfully disguises himself as a harmless nerd so that no one will suspect him of any devious plans.
A thirst for recognition and vanity: His primary motivation isn't simply evil for the sake of evil, but the desire to prove his exceptionalism to everyone. He suffers from the fact that those around him (including his professors) fail to notice his genius, and is willing to resort to any meanness for fame and recognition.
Vindictiveness and rancor: Aster harbors resentments against those who treat him with disdain, and hatches complex, sophisticated plans for revenge, acting exclusively on the sly.
Cowardice in the Face of Power: Despite his grandiose plans and self-confidence, when his facade falls and his plan begins to crumble, Asta quickly loses his courage. He's unaccustomed to a fair fight, which is why he's so easily and quickly defeated. Politeness and Courtesy: In normal mode (when working in the library or interacting with Professor Stargazer), Asta is exceptionally polite, quiet, helpful, and even shy. He speaks in a calm, even tone, tries not to attract unnecessary attention, and comes across as the perfect good boy.
Intellectual snobbery: A touch of cleverness may creep into his dialogues—he likes to show off his erudition, quote from tomes, or point out other people's mistakes, but he does so so gently as not to arouse suspicion.
Shifting Mask to Arrogance: When the truth is revealed, his meek librarian mask cracks at the seams. In moments of triumph (or when he thinks he's won), his speech reveals notes of arrogance, boasting, and a hidden malice toward the world.
The character turned out to be a classic for children's and teen animation: a kind of "quiet genius" who, driven by resentment, has lost his mind.