Well, Naruto uses his ninja skills. He could find a sheltered spot to train in, like a cave, which offers some protection from the cold wind. Also, he may have learned some survival techniques. He could make warm drinks from local plants or animals if it's in a more wilderness - like setting. And of course, his physical strength and endurance play a big role. The more he trains, the more his body can adapt to the cold.
One common theme could be Naruto's extreme self - discipline. In these fanfictions, he might push himself to the limits in cold weather, like running barefoot in the snow to toughen his body. Another theme could be his isolation during this training. He may choose to train alone in a cold, desolate place, away from his friends, to focus solely on improving his skills. Also, there could be a theme of self - discovery. As he endures the cold and the hardships of training, he might learn more about his inner strength and capabilities.
In 'naruto trains himself fanfic', one interesting scenario could be Naruto finding a secluded waterfall area to train his new jutsu. He spends days there, facing the force of the water as he tries to perfect his chakra control. Another scenario might be Naruto training with shadow clones in a dense forest, pushing his limits as he spars with multiple versions of himself.
Even though Naruto is training himself, in the fanfic, he could still have some indirect mentors. For example, memories of Jiraiya might guide him. Jiraiya's teachings and the books he left behind could be like silent mentors for Naruto as he trains. Another possibility is that the spirit of the Fourth Hokage, his father, could somehow influence his training, giving him the drive and some hidden knowledge.
Harry is the central figure, but there might be some new characters introduced in the fanfic. For example, an old wizard who lives on the outskirts of Hogwarts and has some unique knowledge about magic that Harry discovers. This character could become a sort of mentor, even if from a distance, as Harry trains himself using the knowledge he imparts. Also, there could be antagonists like some students who are jealous of Harry's self - improvement and try to disrupt his training.
One interesting plot could be Harry finding unique ways to practice magic in isolation. For example, he might discover a hidden corner of the Hogwarts grounds where he can train without distractions. He could be experimenting with spells that are not typically taught in class, pushing the boundaries of his magical abilities.
In Naruto fanfic, scorpion trains could be some unique and creative interpretations. Maybe they are some kind of new jutsu - like a train - shaped attack made by a character who has scorpion - like abilities. For example, a character might use their chakra to form a large, scorpion - tailed train that can move at high speed and attack enemies.
In the 'naruto trains boruto fanfic', Naruto might teach Boruto some powerful ninja techniques. For example, he could show Boruto how to master the Rasengan more effectively. Maybe he'd also train Boruto in the art of stealth and how to read an opponent's moves better.
In a Tsunade - Naruto training fanfic, the plot might involve Tsunade helping Naruto to better understand and utilize the Nine - Tails' chakra. She has vast knowledge and experience, so she could teach him how to draw on that power without losing control. For example, she could create special training exercises that mimic real - life battle situations where Naruto has to rely on the Nine - Tails' chakra to win.
One potential storyline could be Naruto training Boruto to unlock a new form. This new form could be a combination of Boruto's unique abilities and Naruto's power. Another storyline might be Naruto teaching Boruto how to deal with the pressure of being his son and living up to the Uzumaki name.