Appearance:
Kiyomaro is fairly tall and appears to have golden eyes and untidy brownish-black hair. He ordinarily wears his signature outfit, a school uniform. But he has been seen in different jackets and shirts multiple times. He is considered to be fairly good-looking.
Personality:
Kiyomaro at first was aloof and smart, to the point of even outsmarting the teacher during class. He is a highschool prodegy with a IQ of 170.The main reason for his aloofness was mainly because of his intellect, which made him feel mentally superior to his teachers and fellow students. Which seperated him from the group and then he felt too smart to be in there with "naive" or "idiotic" students, and because of that they discriminated and made fun of him (which Kiyomaro respond by saying that "I stopped caring about what people say/said about me a long time ago,").
He went as far as skipping school on a regular basis to do introverted activities in his room, like reading novels, literature, and other book types and the only time he went outside is to go to a botanical garden as revealed in episode 7 to be in peace in case he and his mother were to argue.
Kiyomaro takes great pride in his "Genius Intellect" and has used it to his advantage in fights, such as putting his opponents in a certain area (due to the trajectory of Zatch's attacks, therfore utilizing a brilliant strategy) or knowing how and when to make use of Zatch's offense and defense to overcome any situation making him a quick thinker.
He's been shown to tutor Suzi and his other friends at his house in his room and in episode 37 he was shown to be able to fix an elevator by moving wired around.
Even though Kiyomaro was aloof he didn't have a cold-heart, he (like Gash) is disgusted with people and mamodo who gets joy out of manipulating or torturing others. He also hates those who use mamodo to commit crimes as revealed in episode 3. He would even go out of his way to help those who were discriminated like him and even protect his friends (mostly Suzy.)
From time to time Kiyomaro can be sly, mean, short-tempered, and mildly sadistic, for example when he tricked Zatch into confronting the bullies of the school on top of the roof, promising to come to his aid.
Another time is whenever Naomi tries to chase Zatch and Kiyomaro tells him have fun, and he leaves him at home when he goes to school and even tells Ponygon to leave his house and never return when he attacked or made fun of him.
Despite that he has also shown to be in tears if Zatch's book was burned and would do whatever he can to prevent that from happening (powerfully implying that he does care about Zatch and the times they had together).
Love Life:
Kiyo has shown to have a crush on Megumi. Such instinces have been shown such as when Apollo teased him for stating that he brought his "girlfriend" on the trip to stop the past demons, he was flustered and so was Megumi (to the point her face turned completely red).
Kiyomaro even blushes many times when talking to Megumi and was rather bashful when telling her to hurry up with the books, but fine yelling at Tia and Gash.
Whenever Megumi is scared or startled, she accidently at times hugs Kiyo and it makes him bashful. Even Megumi reciprocrates this crush as she too has feelings for him, such as teasing Suzy that the two have a secret together only they know. She even wanted to do CPR on him when he needed to be brought back to life, albeit very bashful (something which Tia called a "chance" for Megumi to kiss him).
He also shown to have some feelings for Suzy, but only more as a friend due to him appreciating her being nice to him and his friend. He even offers to tutor her at times if she needs it. He's oblivious of her obvious feelings for him and usually views her as a clutz and niave, but kind and caring. He even kept her lock she gave him before they went to fight Faudo and even remembered her before he almost died. He does usually tend to be annoyed by her childishness and lack of being able to do anything right and her constantly medling. Nevertheless, he is protective with her and tries to keep her out of battles as much as possible and views her as a close friend.