Vivi would likely feel a great deal of guilt. She might blame herself for putting Luffy in harm's way. After all, he got hurt because of her. This guilt could drive her to be more proactive in helping him recover.
Rayleigh would be a great candidate. He's an experienced pirate and has already trained Luffy for a while. He has a lot of knowledge about the world of pirates and could give Luffy a talk about the deeper secrets of the Grand Line or how to deal with the powerful enemies that lie ahead.
The theme of friendship also stands out. The fanfictions often depict how Luffy's friends comfort him when he's hurt. They might share their own past traumas or offer words of encouragement, highlighting the importance of the relationships within the crew.
Perhaps Nami is under a curse. The curse makes her see Luffy as a threat, even though he's not. So, she ends up hurting him because she's compelled to by the dark magic of the curse until the crew can find a way to break it.
Well, in a fanfiction plot, Nicole could be hurt while trying to protect her partner. For example, if there's a bomb threat in a building where they are. Nicole would shield her partner from the blast, resulting in her getting seriously hurt with burns and fractures. Or perhaps she gets into a car accident while rushing to a crime scene because of a mechanical failure in her vehicle.
One possible plotline could be that Tohru gets physically hurt during an accident while helping out at the Sohma house. Maybe she's climbing a ladder to fix something on the roof and slips, resulting in a sprained ankle or a cut. Another could be that she gets emotionally hurt when she overhears some of the Sohma family members saying unkind things about her, not realizing she can hear them. It could make her question her place in their lives.
Yuki would likely be very concerned. He has a soft spot for Tohru and would probably rush to her side, trying to find a way to help. He might even blame himself if he thinks he could have prevented it. Kyo, on the other hand, would initially be angry, but that's just his way of showing worry. He would be more hands - on in getting her the help she needs.
Physical hurt might come from a powerful magic spell. Let's say an evil sorcerer casts a spell that drains Yami's energy and causes him pain. His struggle to overcome this and regain his strength could be a central part of the fanfiction.
It could be about Luffy having an important conversation. Maybe it's about his dreams, his crew, or some kind of revelation he has. Without reading it, it's hard to say exactly.
I'm not sure if there is such a specific fanfiction. There are a vast number of fanfictions out there, but this particular concept might be quite rare or not in line with the general tone of the 'One Piece' series. Fanfiction often explores different relationships and scenarios, but this one seems rather out - of - the - ordinary considering the nature of the characters in the original work.