Well, it could be about an army within the Naruto universe that is involved in some sort of killing spree in a fan - created story. It might feature new characters or a new plotline that focuses on this 'army killer' concept.
Themes of loyalty and betrayal could also be present. There could be a situation where members of the army are betrayed by their leaders, and this leads to the rise of the 'army killer'. Or it could be that the 'army killer' has to deal with their own loyalty issues, such as whether to side with the village or go against the army for a greater good. Additionally, the theme of friendship could play a role, like if the 'army killer' has friends who help them in their mission.
I'm not entirely sure as I haven't read that specific 'fanfic'. It could potentially be a story where Naruto has some sort of encounter with an army and there are killings involved in a fictional scenario created by the fanfic writer.
First, check the official Naruto fan communities. Sometimes, fans share their fanfics within these communities. Additionally, websites dedicated to anime and manga fanfiction are your best bet. However, make sure to follow the rules and regulations of these websites while searching for 'naruto the army killer fanfic'.
Well, he might use his powerful jutsu like the Rasengan. He could also summon his toads to help him out in the battle against the army. Maybe he uses his shadow clone technique to confuse the enemy and then strike them when they're vulnerable.
Well, he might start by using his charisma. Naruto has always been good at making friends. He could reach out to old allies from his village, like Shikamaru and Choji. Also, he might convince some of the outcast ninja who have been mistreated in other villages to join him. His reputation as a hero who saved the world would surely attract a lot of people.
Perhaps it's for exploration. Naruto is always curious about the world outside. The robots can be sent to explore dangerous or uncharted areas where it might be too risky for humans to go. They can collect information and report back to Naruto.
Maybe Naruto has some knowledge from an unexpected source. For example, he could have met a wandering inventor who taught him the basics of robotics. With his determination and quick learning ability, he then starts building the robot army. He might also use his chakra in some unique way to power or control the robots.
Well, Naruto himself would probably be really excited. He'd be running around the military base, trying to make friends with everyone. His positive attitude might initially seem out of place in the strict military environment but could also start to change the atmosphere, making it more lively.