The main character, a bespectacled first grade boy who is aiming to become an excellent ninja. Unfortunately, he often gets distracted and prefers to goof off with his friends Kirimaru and Shinbei.
One of Rantaro's best friends. He is an orphan who lost his family and home during a war, and now makes a living doing various part-time jobs. When school isn't in session, he lives with Doi. His primary interest is being obsessed with earning money.
A rich merchant's son, who quickly became friends with Rantaro at the beginning of the series. He is overweight, a bit slower when it comes to thinking, and often has to be corrected by his friends. Nonetheless, he possesses great power and strength.