11-year-old Kenichi Mitsuba is an average kid who goes to secondary school and struggles with his studies, he is very stubborn and is very lazy and therefore always ends up frustrating his parents and teacher. Meanwhile a little ninja named Hattori Kanzo befriends Ken'ichi. Hattori is now a part of the Mitsuba family along with his brother Shinzo, and his ninja dog, Shishi-Maru. Hattori helps Kenichi with his problems, and constantly keeps an eye on him, as a good friend. Yumeko is portrayed as Ken'ichi's love interest. Kemumaki, a Koga Ninja and his ninja cat kagekiyo always trouble Ken'ichi. Ken'ichi asks Hattori to take revenge. Although Hattori is a good friend, Ken'ichi sometimes fights with Hattori due to misunderstandings created by Kemumaki. Sometimes Jippou, Togejirou and Tsubame helps him.