Nicolas Sarutobi, also known as Nikumaru Sarutobi in Japanese, is a seventeen-year-old student at Ninja High School, an institution dedicated to ninja training. His name Nikumaru, meaning "meatball," reflects his short stature and chubby build. Despite this physique being unconventional for a ninja, he wields exceptional combat skills. His signature move is the "kamikaze" technique, a whirlwind attack generated by spinning his feet rapidly, showcasing unexpected agility and forming a core part of his abilities.

He attends the academy with Mandoline (Mako Kiriga in Japanese), the director's daughter. Their bond, formed in childhood, has grown into a mutual romantic attachment. Mandoline exhibits strong possessiveness, reacting negatively when other girls interact with Nicolas, a dynamic shaping many of their shared experiences. Nicolas's school life centers on defending Ninja High against rival institutions, particularly the neighboring Scorpion Academy, which trains future international spies. Students from this rival academy frequently attempt sabotage, leading to recurring confrontations.

Nicolas participates in various missions and school activities, including athletic competitions, baseball matches, treasure hunts, and winter expeditions. These events highlight his development as a ninja and his relationships with classmates. His personal growth faces tests, such as strict diets aimed at improving his physical condition, though his fundamental traits remain consistent.

Beyond the original series, Nicolas appears in the manga revival "Sasuga no Sarutobi G," where the "G" signifies a global approach. In this modern reinterpretation, he competes in the "Way of the Ninja Academy," engaging in intense battles to achieve the title of "Ninja Master." This iteration maintains his core characteristics—his physical appearance, ninja abilities, and dynamic with Mandoline—while placing them in a contemporary setting.