Obviously Naruto himself is extremely popular. Since the fanfiction is about his intense training, he is the central focus. Sasuke is also popular. His rivalry with Naruto often means he is included in training scenarios, either as a partner sparring with Naruto or as someone Naruto is trying to outdo. Kakashi is another popular character. As Naruto's teacher, he is often involved in guiding Naruto through his intense training.
In Naruto intense training fanfiction, Naruto is without a doubt the most prominent character. However, characters like Jiraiya also gain popularity. Jiraiya is Naruto's mentor in many aspects, and his knowledge and skills play a big role in Naruto's training in the fanfiction. Shikamaru can be another popular character. His intelligence can be used to strategize during training, or he might be observing Naruto's training and learning from it in his own way.
Obviously, Naruto is a top choice as he has so much potential for growth and development in training. Sakura also appears frequently as she is constantly striving to improve her skills. Rock Lee is another common character in these fanfictions because of his intense dedication to training and his unique fighting style. His training methods can be really interesting to explore in fanfiction.
One common theme is self - improvement. Naruto is always striving to get stronger in the original series, and in fanfiction, this is often amplified during intense training arcs. Another theme could be friendship. His friends might join him in training, and their relationships are deepened through shared hardships. Also, the theme of surpassing limits is popular. Writers like to show Naruto breaking through what was thought to be his maximum potential during these intense training scenarios.
Well, Naruto is at the core of these fanfictions. But there are others too. Rock Lee can be part of it. His own training methods, which are based on extreme hard work, can inspire the kind of brutal training Naruto might go through. Also, Orochimaru might be involved in some darker - themed fanfictions. He has his own motives and his knowledge of forbidden jutsu could lead to some really intense and dangerous training scenarios for Naruto, although this would be in a more morally ambiguous kind of story.
Sakura is often a popular character in these types of fanfics. Since she is a kunoichi herself in the original Naruto series, it's easy to write about her further training. Hinata can also be a main character, as her gentle yet strong nature can be explored more during kunoichi training.
Marinette and Adrien are the most popular. Marinette as Ladybug has a lot of room for growth in training stories. She can learn new ways to use her Lucky Charm and improve her combat skills. Adrien as Chat Noir is also a favorite. His charm and acrobatic abilities can be developed further in training scenarios.
Robin himself is obviously very popular. Then there's Batman, as his mentor. Aqualad is also often featured as a friend and teammate. They are important characters in the Young Justice universe and play significant roles in Robin's training stories.
Naruto is often very popular. His outgoing personality and determination make him a natural fit for the rockstar world. Fans love to imagine him on stage, rocking out and inspiring the crowd.
Kakuzu is another character that can be popular in these fanfictions. His unique ability to have multiple hearts and his money - loving nature can add a touch of humor or be explored in more serious ways in relation to the Akatsuki's goals and activities.
Naruto himself is often a popular character in such fanfictions. His popularity in the original series makes him a natural focus for new and cybernetic - themed storylines. Sasuke is also quite popular as fans like to explore how his Sharingan could be enhanced with cybernetic elements.
Naruto himself is often a central and very popular character in these fanfictions. Since it's about his rebirth, readers are interested in seeing how his character evolves differently.