Kazuhiko Hanawa is a male character and a third-grade elementary student who is a classmate of the series' protagonist, Momoko Sakura, often called Maruko. He lives in a large mansion and comes from a wealthy family, a status that is immediately recognizable from his distinctive and much more formal attire compared to his peers. His typical outfit consists of a cream or white collared shirt, an indigo waistcoat, an orange-red tie, black shorts, white socks, and black shoes. During the summer, he changes into a sailor-style uniform with a white shirt, a blue neckerchief, and matching shorts. He has neatly styled brown hair that is usually swept to one side. His parents are frequently overseas due to business obligations, so he often resides in his family's home with a butler who drives him to school in a limousine.

Hanawa carries a polished and elegant manner of speaking that reflects his privileged upbringing. He addresses most of the girls and occasionally the boys in his class as baby, and he tends to focus conversations on positive subjects. While his mannerisms can come across as somewhat snobbish, particularly when he references his own possessions or experiences that his classmates lack, he is not portrayed as unkind. He is shown to be a generous and compassionate child, often sharing his good fortune with others. For example, he frequently brings back souvenirs for the entire class from his overseas trips, such as miniature Eiffel Towers from a vacation to Paris, and he hosts holiday parties at his large home for Halloween and Christmas. He is also depicted as helpful, like when he lent Maruko his four-wheeled bicycle so she could practice riding and gave her encouragement. He helped make a wish come true for a friend of his classmate's grandfather by arranging an opportunity to learn how to dine at a French restaurant.

Despite his wealth and charm, Hanawa is notably concerned with maintaining his image and reputation, expressing visible shock or dismay when faced with embarrassing situations, such as stepping in something unpleasant, cleaning up a mess, or having his poor handwriting criticized. Beneath his sophisticated exterior, there are hints that he may experience some loneliness due to the long-distance absence of his parents, which adds a layer of nuance to his character.

In the story, Hanawa serves as a contrast to the more modest and somewhat chaotic life of his classmate Maruko. While Maruko occasionally finds his habit of showing off his luxurious lifestyle a bit annoying, she considers him a good friend. Their friendship is marked by Hanawa's subtle and often-unnoticed romantic interest in Maruko. He has shown special attention to her in several episodes, such as requesting chocolate from her on Valentine's Day, giving her roses for her birthday, and preferring to spend time with her over other girls. This dynamic is observed by other classmates, like Hanako Migiwa, who views Maruko as a rival for Hanawa's attention. His key relationships are primarily with his classmates, as his family is largely absent from daily life.

Hanawa possesses a wide range of talents and abilities that are cultivated by his family's resources. He takes weekly lessons in English and French, as well as piano, violin, and Indian philosophy. He is fluent enough in English to direct a lost foreign visitor to a bus station, much to the amazement of his friends. He is a fan of actress Audrey Hepburn and is said to own her autograph. His favorite foods include sushi, Italian cooking, shrimp coquille, and sweet and sour pork, and his favorite sport is tennis. He is also skilled at playing cards and treasures a Swiss clock and letters from his parents sent from abroad.