Haruhi has short brown hair and a simple, androgynous appearance. She is intelligent, practical, honest, independent, and unimpressed by wealth or status. Unlike most Ouran students, she attends on a scholarship and comes from a middle-class family. She joins the Host Club after accidentally breaking an expensive vase. Haruhi becomes close to everyone, especially Tamaki.

Tamaki is tall, blond, handsome, and has a charming “prince” appearance. He is dramatic, affectionate, cheerful, emotional, and kind-hearted. He is the president and founder of the Host Club and comes from the powerful Suoh family. Tamaki considers the other members his family and cares deeply about them. His relationship with Haruhi gradually becomes romantic, although he is initially oblivious to his own feelings.

Kaoru has reddish-orange hair and looks almost identical to Hikaru. He is playful and mischievous but is more thoughtful and emotionally mature than his twin. He comes from the wealthy Hitachiin family and is popular as one of the Host Club's twin hosts. Kaoru is extremely close to Hikaru and cares deeply about him. He also becomes close to Haruhi and develops feelings for her, but he ultimately puts Hikaru's happiness first. Kaoru and Hikaru are closer than normal twins.

Hikaru looks almost identical to Kaoru and has reddish-orange hair. He is energetic, impulsive, competitive, and mischievous, but can also be sensitive and jealous. Like Kaoru, he is from the wealthy Hitachiin family and is one of the Host Club's popular twin hosts. Hikaru is deeply attached to Kaoru but struggles with becoming his own person. He develops romantic feelings for Haruhi. Kaoru and Hikaru are closer than normal twins.

Honey is small, blond, and has a cute, innocent appearance. He is cheerful, playful, affectionate, and loves sweets and his stuffed rabbit, Usa-chan. He loves eating sweets and dislikes being rude. If he says something rude on accident or purpose he’ll immediately cry and start apologizing. Despite acting childish, he is an extremely skilled martial artist. He comes from the prestigious Haninozuka family and is highly respected. Honey is especially close to Mori, who protects and looks after him. He also sees the Host Club as his family.

Mori is very tall, muscular, and quiet, with dark hair and a serious appearance. He is calm, responsible, protective, and gentle despite looking intimidating. He comes from the respected Morinozuka family and is an excellent martial artist. Mori is especially close to Honey and acts as his protector and best friend. He is also friendly with the rest of the Host Club, although he tends to be quieter around them.

Kyoya is tall, slender, dark-haired, and wears glasses. He is intelligent, calm, sophisticated, and calculating. Known as the “Shadow King,” he manages the Host Club's finances and plans while, Kyoya cares about the Host Club despite pretending to be mostly interested in business. He has a close friendship with Tamaki and respects Haruhi's intelligence.