Jasminka Antonenko is a student at the Luna Nova Magical Academy and a member of the group led by the boisterous Amanda O'Neill, alongside the quiet inventor Constanze. She is a tall, plump girl with long, pale pink hair that she wears in two distinctive braided pigtails tied with bows. Her most characteristic physical feature is that her eyes are almost always drawn as relaxed, closed slits, which rarely open. Jasminka is a cheerful, gentle, and remarkably peaceful individual who loves sweets and a quiet life more than anything else. Her constant, easygoing smile and her habit of eating snacks continuously, even during class, define her public persona. She is rarely, if ever, seen without some form of food, such as chips, donuts, or fruit, and is known to be a "big eater." Her calm and laid-back nature makes her seem almost unflappable; she rarely gets angry or shows signs of being bothered by the chaos that often surrounds her friends, to the point where it can be difficult to tell if she is paying attention. However, this relaxed demeanor belies a deep-seated generosity, as she is always willing to share her treats with others, using food as a way to connect with, cheer up, and comfort her friends and even strangers.

Jasminka comes from Russia, though the specifics of her family background are not explored in the main narrative. A key element of her backstory, revealed in supplementary manga adaptations, is that she accidentally ate a magical creature called a Hunger Faery as a child. This faery took up residence in her stomach, forcing her to eat constantly to keep it appeased. This unique condition explains her otherwise inexplicable and insatiable hunger, which is not merely a preference but a physical necessity. She first appears in the film The Enchanted Parade, where she is punished for her incessant snacking and is assigned to help organize the annual town parade alongside Amanda, Constanze, and the protagonist Akko Kagari. In this event, her love of snacks becomes central to the parade's theme, with her "Happy Flavor" chips inspiring the "Happy Time" concept that ultimately saves the day.

Within the main television series, Jasminka continues to be a constant but quiet presence, always appearing as part of Amanda's trio. Her exact motivations are simple and consistent: she seeks peace and enjoys her snacks. This drive, or lack of a more ambitious one, often gets her into minor trouble with the school faculty, who consider her a "problem child" for eating during lessons. However, her role in the story is that of a supportive and reliable friend. She willingly assists the main characters whenever they need help, whether it is searching for a missing classmate, helping with heavy chores like laundry when the Sorcerer's Stone is stolen, or acting as a counselor during the Samhain Festival. While she never receives a dedicated "focus episode" in the anime, her loyalty and willingness to help are unwavering.

Jasminka's key relationships are primarily with her two roommates, Amanda O'Neill and Constanze. She is very close to Amanda, who affectionately nicknames her "Yasna." They, along with Constanze, form a tight-knit trio of troublemakers, each with their own unique brand of rule-breaking. Jasminka is also shown to have a decent knowledge of Constanze's secret workshop and often helps the smaller girl by carrying her or providing physical support for her inventions. She has a warm and fond relationship with Akko, regularly offering her food and sharing her positive energy. In turn, Akko is a caring friend; in one manga storyline, Akko even tries to put Jasminka on a diet, only to learn the truth about the Hunger Faery and tearfully apologize. By the end of the series, Jasminka is even shown sharing a friendly moment with Hannah England, a former antagonist, calmly eating sandwiches together, which suggests her gentle nature helps build bridges across the student body.

Jasminka's character undergoes subtle development, not in changing her personality, but in revealing hidden depths. Despite her placid exterior, she is capable of great determination and possesses significant power. One of her most surprising traits is her immense physical strength, which is showcased when she effortlessly carries heavy objects, jumps from brooms while holding Constanze, or handles heavy lifting during physical tasks. Her magical abilities are also considerable. She is highly skilled in culinary magic, able to enchant sweets and use spells to enhance the flavor of food, earning high marks in practical exams. She is proficient in standard magic like flying on a broom and telekinesis. One of her most unique and visually striking spells is the Graviton Omega, which allows her to inflate her body into a near-perfect sphere, dramatically increasing her weight so she can roll over obstacles, weigh things down, or crash into enemies like a cannonball. In the climactic final episodes, she demonstrates her resolve by being the first to separate from her friends during a dangerous mission, using all her remaining magic power to give their combined broom a powerful boost. This act reveals that beneath her calm and snack-loving exterior, Jasminka is a deeply reliable and courageously selfless witch.