Her relationship with Natsu would likely change significantly. Since Natsu is a dragon slayer, they might become rivals in a friendly way, constantly trying to outdo each other in terms of dragon slaying skills. But they could also team up more often, combining their unique abilities to face greater threats.
Lucy's new power would bring a shift in her relationships. With Happy, he might be constantly curious about her Celestial Dragon Slayer magic and pester her with questions. The guild as a whole would view her in a new light. Some might be jealous of her newfound power, while others, like Levy, would be excited to research more about it. This could lead to new friendships forming as Lucy shares her experiences with others in Fairy Tail, and also cause some minor frictions as she has to navigate through the different reactions to her power.
Bulma's relationship with the other Z - fighters would also be different. They would no longer see her as just the tech - support person. Now, she could be a front - line fighter. They might be in awe of her new powers at first, but then they would start to rely on her more in battles, and she would have to learn how to work with them in a more combat - oriented way.
His relationship with Bakugo might change. Bakugo, who used to look down on Izuku, might now be a bit jealous or even more competitive as Izuku's Dragon Slayer quirk is very powerful. With his friends like Uraraka, she could be in awe of his new quirk and support him more actively in battles. Izuku might also attract the attention of some of the more powerful heroes in training, who want to team up with him because of his unique ability.
Hiccup's relationship with his father (if his father is still alive in the fanfiction) would be complex. His father might be proud of him for achieving such a powerful status, but also worried about how the other tribes would react. Hiccup would also have a different relationship with the dragons in general. He would no longer be just a friend to them, but a leader, a dragon god. This could lead to some dragons being more submissive to him, while others might test his new authority.
His relationship with Sasuke would be very interesting. Sasuke might be initially suspicious of Naruto's new form, but eventually, they could bond over Naruto's struggle to control his powers and use them for good. It could be a new level of rivalry and friendship.
When Fem Percy becomes a goddess, her relationships take on a whole new dimension. Her friends from her mortal life would see her in a different light. They would respect her more, but also might be a bit intimidated. For example, if she used to be part of a close - knit group, they might not be as casual with her anymore. Her relationship with her family could also change. Her parents, if they are still around, would be proud but also a bit in shock. In the world of romance, if she was in a relationship, her partner would need to adjust. They might feel like they have to prove themselves worthy of being with a goddess. And Percy herself would have to figure out how to balance her relationships with her new responsibilities as a goddess.
In terms of her relationship with Gray, there could be a new dynamic. If'si' reincarnated as Lucy, she might be more competitive with Gray, which could lead to some interesting interactions. Her relationship with the celestial spirits would also change. She could become more like a mentor to them, teaching them new things from her past life or experiences. Also, her relationships with other guild members would likely expand. She might form closer bonds with some of the more reserved members of Fairy Tail, bringing them out of their shells.
Her relationship with other celestial spirit users could be affected. They might be jealous of her new power, or they could see her as a symbol of hope for all celestial spirit magic. If there are any anti - celestial spirit groups in the fanfiction world, they would likely target Lucy more. This would put a strain on her relationships as she has to deal with the added danger. On the other hand, it could also bring her closer to some of the more powerful and reclusive celestial spirit users who are interested in the Aquarius power and what it means for the future of their magic.
If Cortana becomes human, her relationships would change drastically. Her relationship with her former AI colleagues or creators would become more complex. She would no longer be just a program they can control or upgrade. Instead, she would be an equal, which could lead to some power struggles or awkward moments.
His relationship with his guildmates would likely become more complex. They might look at him with a mix of awe and a bit of fear. His closest friends would still support him, but they would have to get used to his new - found power.