Definitely Naruto. He's always been there for Sakura, no matter what. He would use his Nine - Tails chakra if he had to in order to save her. Sakura's female friends like Ino could also play a role in her rescue. Ino is a skilled ninja in her own right and has a deep friendship with Sakura. And don't forget Tsunade. As the Fifth Hokage and Sakura's mentor in the medical field, she would do everything she could to save Sakura's life.
One common plot could be a battle where Sakura is severely outnumbered. For example, she might be facing a horde of powerful enemies alone while her comrades are occupied elsewhere. Another plot could involve a dangerous experiment gone wrong. Maybe she was trying to develop a new medical jutsu but something in the process backfired and put her life in jeopardy. Also, it could be a situation where she sacrifices herself to protect someone she loves, like Naruto or Sasuke, and almost dies in the process.
Sakura would likely be devastated. She has always cared for Naruto, even if her feelings have been complex at times. Her crying shows the depth of her fear of losing him. It could make her feel guilty for not being strong enough to protect him.
In this kind of fanfiction, there could be various scenarios. Maybe Tails gets into a fight with a really powerful enemy, like a new super - villain. The villain might have some sort of weapon or power that nearly defeats Tails. For example, a weapon that can disrupt his flight or his mechanical abilities.
Fanfictions about Naruto being neglected and nearly dying can be quite intense. Some might depict him being pushed to the brink by the lack of support from the village. For example, he could be deprived of proper training or basic necessities. However, these situations usually lead to Naruto's character growth in a different way than in the original series. He might form unexpected alliances with outcasts or find new powers within himself.
One possible plot development could be that Sakura's tears somehow give her a newfound strength or resolve. Maybe she decides to train harder to protect Naruto in the future. For example, she could seek out a powerful teacher or a hidden jutsu to become stronger.
In some fanfictions, Hermione could be in a situation where she's exploring a dangerous, ancient magical ruin. There could be a series of traps, and she almost dies when she accidentally triggers a deadly one. Her intelligence and quick thinking, along with the help of her friends, might be the only things that save her in the end.
One scenario could be that he is poisoned by a mysterious potion slipped into his food in the Great Hall. Maybe a Death Eater sympathizer among the students manages to do this.
One possible reason could be a misunderstanding. Maybe Sakura is under the influence of some dark magic or mind - control in the fanfiction, which makes her lose her rational judgment and attack Naruto. Another reason might be a strong emotional outburst. For example, if she discovers something she believes Naruto has done wrong, but in fact it's a misinformation, and her anger gets the better of her, leading to her almost killing Naruto.
There's no way to know the author just from this title. Fanfiction is a vast world with countless creators. It could be a relatively unknown writer who just wanted to explore this unique and somewhat dark concept. Maybe it was written by someone who was experimenting with different ways to tell a story within the existing fictional universe related to Sakura.