Kazuhiko Hanawa is a third-grade elementary school student and a recurring character. He lives in a large mansion and is chauffeured to school in a limousine by a family butler, a lifestyle that sets him apart from his classmates. His parents are frequently overseas for business, meaning he spends much of his time without their direct presence, despite the material luxury that surrounds him.

Physically, Hanawa is easily recognized by his brown hair, which is meticulously styled and swept to one side. His attire is consistently more extravagant than that of his peers; his typical school outfit includes a cream or white long-sleeved collared shirt, an indigo waistcoat, an orange-red tie, black shorts, white socks, and black shoes. During warmer months, he wears a sailor-style uniform consisting of a white shirt, a blue neckerchief with white borders, and matching blue shorts.

Hanawa carries himself with a cultivated posh air and uses elegant, refined language. This demeanor can sometimes appear snobbish, particularly when he casually mentions his possessions or international experiences that are far beyond the reach of his friends. He has a habit of addressing most of the girls, and occasionally the boys, in his class as baby. In conversations, he tends to focus on positive aspects rather than negative ones.

Despite this privileged exterior, Hanawa is not an unkind character. He is notably generous, often sharing what he has with his schoolmates. For instance, he regularly brings back souvenirs, such as miniature Eiffel Towers, from his trips abroad and invites his entire class to his house for festive celebrations like Christmas and Halloween. He is also helpful, and on several occasions has assisted his friend Maruko, such as when he lent her a bicycle with training wheels to help her learn to ride. He is generally willing to use his resources and knowledge to fulfill the wishes or needs of others, demonstrating a genuine concern for the people around him. However, he is deeply concerned with maintaining his sophisticated image, reacting with visible shock or dismay when caught in an embarrassing or undignified situation, such as stepping in mud or being told his handwriting is illegible.

Within the story, Hanawa's role is often defined by his relationship with the main character, Momoko Sakura, who is known as Maruko. While Maruko can sometimes find his elite habits and tendency to show off his wealth annoying, she ultimately considers him a good friend. There are subtle hints that Hanawa may harbor a gentle crush on Maruko. He has been known to request chocolate from her on Valentine's Day, give her roses for her birthday, and choose to spend more of his free time with her than with other girls, though Maruko herself does not seem to recognize these gestures as romantic interest. This dynamic creates a source of comedic tension, as another classmate, Hanako Migiwa, who has feelings for Hanawa, views Maruko as a romantic rival.

Hanawa's abilities and interests are extensive and reflect his affluent upbringing and international exposure. He takes weekly lessons in English, French, piano, violin, and Indian philosophy. His command of English is particularly strong, fluent enough to give directions to a lost foreign visitor, though he admits to still having gaps in his vocabulary for more complex subjects. He greatly enjoys sharing stories about his overseas trips and discussing cultures from around the world. His favorite foods include sushi, Italian cuisine, shrimp coquille, and sweet and sour pork. He is an admirer of Audrey Hepburn and is proud to own her autograph. He is also skilled at playing tennis and card games. Among his most prized possessions are a Swiss clock and the letters he receives from his parents while they are abroad. Underlying his polished exterior, there are occasional hints of loneliness or a longing for deeper connection, likely stemming from the physical absence of his parents, which adds a subtle layer of depth to his otherwise glamorous character.