Kemuzou Kemumaki is the main antagonist of the manga and anime Ninja Hattori-kun. He's a Koga - Ninja. He's Hattori's arch-rival. He lives in a condominium with his cat Kagechiyo, and happens to be the opposite of Kenichi. He loves Yumeko, but the reason why he dislikes Kenichi is because he loves her too. However, he is scared of some of Hattori's ninja techniques, and can easily be intimidated by him. He does have a soft side though.
as Hattori's arch-nemesis, Kemuzou uses many disguises to fool him, but truth always came out and Kemuzou's plans fails.