Tenma is shown to have a very naive and positive personality, and she is annoying to some. She usually puts her positive thoughts with her determination to get close to Ooji Karasuma. Tenma worries she has no good qualities, as she can only think of the bad qualities she has. She is quite childish, but really wants to be thought of as a woman. Tenma has a habit of misunderstanding and misinterpreting situations, even obvious ones. She is quite naive and gullible, as she is willing to trust anyone. Her pigtails adjust according to her mood.

Currently in love with Tenma The bane of Harima's existence. No matter how hard he tries to chase after Tenma, he inevitably ends up in misunderstandings with Eri. Harima and Eri have numerous misunderstandings over the course of the two seasons of anime, the manga, and the OVAs. Despite their constant bickering, Harima and Eri work extremely well as a team. Their love/hate relationship has formed the basis of the ever-popular Flag Faction. Harima refers to Eri by the nickname "Ojou," meaning something along the lines of "Madame" (teasing her social status). In the English dub, he refers to her as "Rich Girl."

Even though Eri was asked out by many guys, only one managed to capture her attention and her heart. Almost all characters she interacts with or was able to get closer with, encourages Eri's feeling for Harima. Some even encourage her to confess her feelings to him, like Yamato's friend mentioned Eri's feelings for Harima is known throughout school. Some feel that Eri and Harima could be a perfect couple since they act very natural together. Shes also a tsundere

Always kind and considerate, he always seems to care for the well-being of others (namely Tenma Tsukamoto), and his usual thoughtfulness can only be disrupted by his love for curry, which is Karasuma’s favorite food and the true love of his life. Even though Karasuma gives the impression of being an anti-social loner, he enjoys participating in every event of his class, be it as a coach, referee, DJ, or playing with the band. Strangely enough for some reason, he never seems to take part in sports events as a competitor, and usually takes on a behind-the-scenes role, despite his little-known physical prowess. Karasuma is a really quiet, yet interesting character. He seems to be really caring around Tenma, and he also seems to act like a teacher, always giving out little clues to be found out later, at the moment when he gives Tenma a turtle to find out her true talents.