The era is the turbulent Sengoku period. Rantaro, born into a family of low-ranking ninjas for generations, enrolls in the Ninjutsu Academy on his father's advice, aiming to study and become a top elite ninja. However, along with his friends Shinbei and Kirimaru, his grades are consistently failing. Make-up exams and remedial classes are the norm. The teachers are constantly kept on their toes by this trio who try hard but often end up spinning their wheels. Yet, trouble always seems to find them. The three combine their limited wits and, before they know it, end up playing major roles in events.