Yang would be completely heartbroken. She'd likely go through a period of intense grief and anger, possibly even blaming herself for not being able to protect Ruby. Weiss would be deeply affected too. She might become more reserved and solemn, vowing to use her skills to uphold Ruby's ideals. Blake would be inspired by Ruby's sacrifice to be more active in fighting against the darkness. She might see it as a call to arms to make Ruby's sacrifice not be in vain.
Weiss would probably be very protective at first. She has always had a bit of a mother - hen side to her, and seeing Ruby in a more vulnerable, deaged state would bring that out. She would likely try to keep Ruby out of trouble and make sure she was taking care of herself.
In such a fanfiction, one possible plot could be that Ruby sacrifices herself to save her friends from a powerful and evil enemy. Maybe she uses her Silver - eyed Warrior powers to their fullest extent, which drains her life force but stops the enemy from harming her team. Her sacrifice could then inspire her friends to carry on her legacy and fight even harder against the forces of evil.
The other characters would be shocked. Weiss would probably be the first to try and figure out what's wrong with Ruby. Blake would be worried about Ruby losing her way, and Yang would be furious. Yang might even go on a solo mission to bring Ruby back, not fully trusting the rest of the team to handle it delicately. The rest of the characters like Jaune and Nora would also be in disbelief and would start planning ways to rescue Ruby.
His friends like Shikamaru would be deeply affected. Shikamaru, who had always respected Naruto's tenacity, would be at a loss. He might think about all the times Naruto pushed forward despite the odds and feel guilty for not being able to prevent his death. Hinata would be inconsolable. She had deep feelings for Naruto, and his sacrifice would shatter her world. The other ninja from different villages that Naruto had befriended during his journey, like Gaara, would also be in mourning. They would see Naruto's sacrifice as a noble act that inspired them to be better protectors of their own villages and to work towards a more unified ninja world.
The other characters' reactions would vary greatly. For instance, Gary, who has always had a bit of a rivalry with Ash, would be shocked. He might initially be in denial but then realize the depth of Ash's selflessness. Professor Oak would be extremely sad and would see Ash as a true hero. The Gym Leaders that Ash has faced and befriended would hold commemorative events in their Gyms. They would talk about Ash's courage and how his sacrifice has left a huge mark on the Pokémon world. His sacrifice would also inspire younger trainers to be more like him.
Well, Shikamaru would be one of the characters who would take Naruto's sacrifice very hard. He had always respected Naruto's determination. His reaction might be to become more serious about his duties in the village, feeling that he needs to step up in Naruto's absence. Hinata would be heartbroken too. She had deep feelings for Naruto. She might struggle to come to terms with his loss but also find strength in his selfless act. And all of the Konoha 11 would be united in their grief, vowing to protect the village and each other more fiercely in Naruto's memory.
The other members of Team RWBY would be deeply affected. They would start to question their own abilities and the purpose of their fight. Some might withdraw into themselves, like a broken Weiss who shuts out the world for a while. Yang, on the other hand, could become reckless in her pursuit of vengeance, endangering herself and others. Blake would try to hold the team together, but she would also be mourning privately. The other friends and allies in the RWBY universe would also be in mourning. Qrow might blame himself for not being there to protect Ruby, and Ozpin would see it as a great setback in the fight against evil.
For Harry, it would be devastating. Hermione has been his rock, his intellectual equal. Without her, he would feel lost and incomplete. He might become more reckless in his fight against evil, as he no longer has her to rein him in.
The Weasleys would be devastated. Bill, Fleur's husband, would feel a mix of gratitude towards Harry and intense guilt for not being able to save Fleur himself. Ginny would be heartbroken, having once had feelings for Harry. Hermione would be in shock and would probably spend a lot of time trying to figure out if there was any way they could have prevented it. Ron would be angry at first, angry at the situation and at the bad guys who put Fleur in danger, but also deeply sad for losing his friend.
With Weiss, their relationship could be more strained at first. Since Weiss has some preconceived notions about Faunus, she might be initially distrustful of Ruby. But as time goes on, they could overcome this. With Blake, they might bond more deeply as they both share the Faunus experience in a way. And with Yang, Yang would be very protective of Ruby, especially if Ruby faced any discrimination because of being a Faunus.