The fanfiction could explore Naruto's loneliness by depicting his isolation during his training. He often has to endure difficult and solitary training sessions. This physical and mental isolation can emphasize his loneliness. Also, in some fanfictions, his loneliness might be shown when he faces discrimination from the villagers. Despite his efforts to be friendly and gain acceptance, there are still those who shun him, which deepens his sense of being alone.
Some fanfictions may show Naruto's loneliness in a more emotional and internal way. They might explore his dreams and how in them he is still alone, even when surrounded by people in the real world. His loneliness could be a driving force for his character development in the fanfiction. For instance, it could lead him to seek deeper connections with others or to find solace in his own strength and abilities.