Obviously Naruto is a main character as it's about his shadow clone. But there could also be Sasuke. Maybe Sasuke discovers something strange about Naruto's shadow clones and gets involved in the mystery.
Kakashi could also be a main character. He is Naruto's teacher and might notice some abnormal behavior in Naruto's use of shadow clones. He could then try to figure out the secret behind them. Also, Sakura might play a role. If the shadow clones are acting differently, she could be the one to first sense that something is off with Naruto and try to help him figure out what's going on with his shadow clone ability.
Another possible main character could be an original character created for the fanfiction. This character might have a special ability to detect or interact with Naruto's shadow clones in a unique way. They could be the key to unlocking the secret of the shadow clones, whether it's a new power, a hidden danger, or a connection to an ancient prophecy.
Well, Naruto is definitely one of the main characters, since it's about him being the master of the shadow clone. There might also be his friends like Sasuke and Sakura. They could play important roles in supporting Naruto's development with his shadow clone abilities or be involved in battles where Naruto uses his jutsu.
In many such fanfictions, Kakashi could play an important role. He has experience with Naruto's shadow clones and could offer guidance on how to control them or stop the incident from getting worse. Also, characters like Jiraiya might show up. Jiraiya could teach Naruto some new techniques to better manage his clones, or he might be involved in uncovering the mystery behind the abnormal clone behavior.
Sasuke is also often a key character in these fanfictions. He might interact with Naruto's shadow clones in various ways, such as training with them or mistaking a clone for the real Naruto during a battle.
Obviously Naruto himself is always popular as he is the one who creates the shadow clone army. Sasuke also often appears in these fanfictions, sometimes as an ally and sometimes as an antagonist to Naruto's use of the clones. Kakashi is another character that is frequently included. His wisdom and experience can play important roles in stories involving the shadow clone army, like training Naruto to better control his clones or using his own knowledge to strategize with the clone - based forces.
Hermione Granger might also be a key character. She could be involved in researching the theory behind the shadow clones and helping Harry control or improve this new form of magic.
One interesting plot could be a shadow clone having its own consciousness and going on a secret mission without Naruto's full awareness. It might discover a hidden power or a long - lost technique.
It could be a rogue ninja who has a special ability to disrupt shadow clones. This antagonist might be jealous of Naruto's ability to use shadow clones for training and wants to stop him. Maybe he has a jutsu that can make Naruto's clones go berserk and attack him instead of following his commands.
Sakura is often paired with Naruto in such fanfictions. Since she already has a complex relationship with Naruto in the original series, adding the element of the female shadow clone can create interesting dynamics. For example, the clone might make Sakura see Naruto in a new light or cause some jealousy.
Obviously Naruto himself would be a main character as the source of the clones. Maybe Sasuke could also be involved, either as an ally or an antagonist in relation to the clone army.
Sakura could be a main character. She might be suspicious of the clone at first, thinking it could be a threat to Naruto. But as the story progresses, she could come to understand the clone's situation and even help in its development.