One way is through pacing. They slow down the story when Naruto is at his weakest, making every moment count. They might also use flashbacks to show what Naruto has to live for, like his friends and his dreams for the village. This makes the readers more invested in his survival. And they introduce unexpected twists, like a false hope of recovery that turns out to be a trap or a new threat emerging just when it seems Naruto might be saved.
They create tension by isolating Naruto. If he's alone and nearly dying, it makes the situation more dire. Writers also describe the environment in detail. If he's in a dark, cold place while on the verge of death, it adds to the mood. And they show the consequences of his possible death, not just for him but for the whole Naruto universe. For instance, how his death would affect the balance of power between the villages or the future of his friends.
Writers create tension by making the danger seem real. They describe Naruto's injuries in detail, like his labored breathing, his weakening chakra flow. For example, if he's been stabbed, they might write about the pain shooting through his body. This makes the readers worry about his survival.
One example could be a fanfiction where Naruto is in a battle against a powerful new enemy. Maybe this enemy has a unique jutsu that can drain Naruto's life force. Another could be a situation where he sacrifices himself to save the village from a massive destruction, like a huge explosion or a powerful curse. There are also fanfictions where he's poisoned and on the verge of death, and his friends have to race against time to find an antidote.
One way is through the reactions of the other characters. If the village leaders start to question whether Naruto can still be a useful ninja, it creates tension. And if his friends are divided on how to help him, that also adds to it. Another method is by introducing new threats that specifically target Naruto because of his weakened state due to his breathing problem. Maybe there's a group that wants to take advantage of his vulnerability.
By making the consequences of their actions towards each other more severe. Say Naruto's actions lead to Ino being seriously injured and she loses her ability to use some of her ninja skills for a while. The fear of whether she will ever regain those skills and the guilt Naruto feels can create a lot of tension in the story. Also, if there are external factors like other ninja clans getting involved in their conflict because of what happened between Naruto and Ino, that can add more layers of tension.
Another way is through the description of Taehyung's own state. If he's in pain but trying to be strong, or if he's confused and hurt by the situation, it makes the readers feel for him. The writers might also introduce some obstacles in his recovery process, like a lack of proper medical facilities or some internal conflicts within the group that delay his getting better. This all serves to create and maintain tension throughout the fanfiction.
By using descriptive language about the attack. If the writer vividly describes the attacker's menacing appearance, like 'The dark - cloaked figure loomed over Hermione, its eyes glowing red as it raised its wand menacingly', it makes the situation seem more dire. Also, showing Hermione's fear and vulnerability, such as her hands shaking as she tries to reach for her wand, adds to the tension.
One way is through time pressure. The writer could set a deadline for Lupin to rescue the kidnapped person, like if he doesn't do it within 24 hours, something terrible will happen to the victim. Another is by introducing obstacles in Lupin's path. For example, the kidnapper has set up numerous traps and guards around the place where the victim is held. And the writer can also build tension by revealing bits of the kidnapper's plan gradually, making it seem more and more menacing.
Writers can create tension by having the fungal infection spread quickly. If it starts infecting more and more characters at a rapid pace, the remaining characters will feel pressured to find a solution fast. For example, if a whole village gets infected overnight, the RWBY team will be in a race against time.
Writers create tension by showing Sonic's pain and struggle. For instance, if he's trying to run but the injury stops him, it builds tension. Also, when his friends are worried about him, like Tails panicking as he tries to figure out what's wrong with Sonic, that adds to the tension.
Writers can create tension by making Naruto's unrequited love a secret that he has to keep. The more he tries to hide it, the more likely it is to be accidentally revealed, which can lead to a lot of drama. They can also show how Naruto's love for Sakura affects his relationships with other characters. For example, if he starts to distance himself from his friends because he's so caught up in his feelings for her, it can create a sense of unease. And finally, the uncertainty of Sakura's feelings can be a great source of tension. The writer can keep the reader guessing whether there's a chance for Naruto's love to be requited or not.