He wears a large pair of round glasses, a black shirt, jeans and black and white sneakers. He is almost bald with only a bit of grey hair on the sides of his head. It is assumed he doesn't shave. For formal wear, he wears a brown tuxedo mask and wears a brown top hat on his head.
He is extremely greedy, sometimes selfish and will do almost anything for money. In episode "Brat Attack" he even sold Ami and Yumi for ten million dollars to give them to a kid, named Timmy, for his birthday. He would always rush to a show just to get money. Also, he is revealed as a cheapskate of the group at times, when it comes to spend money for others including the duo. At the same time, he spends a bit more for himself, like buying comic books with the duo's money for foods in "Rock N Roe". Despite this, Kaz deeply cares for Ami and Yumi and wouldn't live if they weren't around. He despises Jang Keng and Tekirai, because Kaz is a constant victim of their mischief. However, he adores his pet dog Domo a lot.
While he is extremely obsessed with money and money-making opportunities, Kaz barely has any interests into making girlfriends and prefer spending times with Ami and Yumi over that. He also refers that he likes how he looks like, when Ami and Yumi decides to improve his appearance and fashion senses to make him a girlfriend in "Stupid Cupids."
- Most of the time, when Kaz tries to get rid of something or wants something to be done, he uses the contract to make Ami and Yumi do this.
- In the episode Visiting Hours, we find out that Ami and Yumi don't know his last name.
- Some confusion exists about the character and the real life individuals he is based on. During Otakon 2005 where the band appeared as guests, their real life manager was in attendance. When asked what he thought of his cartoon counterpart, he admitted he had never seen it. While playing a clip of the show and seeing Kaz for the first time, he simply laughed and asked why he was so short in the cartoon. However, Kazuo Harada, who is known as the character is named for, was a anime producer who was never directly associated with the band.
- Then-current manager of real-life Puffy AmiYumi, Kimikazu Harada(原田公一), shares overall appearance with Kaz. Ami Onuki's official Instagram has a page with his picture to celebrate his 62th birthday, with hashtags like "#KAZ" and "#hihipuffyamiyumi." The name "Kaz Harada," meanwhile, is appeared in the show's credit and New York Times' article about the show written in July 2004. These could be clues to consider that Kimikazu Harada is a different individual but assumed to be the "real Kaz."
- Kaz appeared in Oldie AmiYumi, even though in real life at that time it takes place, he would die from old age. While his age is unclear in the show, in Stupid Cupids, he said that his appearance has been the same for 30 years. Kimikazu Harada, who is possibly considered as the "real Kaz" for sharing overall appearance and his career being real-life Puffy AmiYumi's ex-manager as well as the name, was around 50 years old when the show was launched in late 2004.
- His design loosely resembles Happosai from Ranma ½.
- Kaz is sometimes a jerk and greedy character, but he’s mostly the show’s butt-monkey.
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