It will change in many ways. For one, Bella may have become more independent during Edward's absence. Edward will have to respect that new - found independence. Also, their love might be deeper now that they've experienced being apart. They'll have to learn to communicate better, as their previous issues led to Edward leaving. There could be a lot of making up and re - establishing of the relationship's boundaries.
Well, perhaps Edward left Bella to protect her from the vampire world, but then he discovers that she's in even more danger without him. He gives up on his noble, yet perhaps misguided, attempt to keep her away. So he returns, and their relationship has to start anew. There could be a lot of tension at first, as Bella has been hurt by his leaving. But eventually, they might find their way back to each other.
I recommend "Quit Deadly Lover (Complete Version)". The female protagonist of this modern romance novel is smart and wise. She's not a weak female protagonist, nor is she a female protagonist who still loves the male protagonist in the end. In the story, the male protagonist was a typical black-bellied man. He was scheming and full of predatory nature. He had a crazy ambition for the female protagonist to pursue power. There were many heart-wrenching scenes, but the female protagonist did not choose to continue to love the male protagonist. Instead, she found her own career and growth. I hope you like this fairy's recommendation. Muah ~๐
The story might take a more somber turn. Snape could become more withdrawn and focus solely on his own pursuits. For instance, he may throw himself into his potions research even more intensely.
Well, Edward's alchemy in DC fanfiction is sometimes a source of mystery to the DC characters. Since they are used to powers like super - speed or telepathy, Edward's ability to transmute objects and substances through complex alchemical arrays is something new. It can also be a tool for him to bridge the gap between the two very different worlds he finds himself in - his own FMA world and the DC world. He might use alchemy to communicate with characters who have different forms of power or to solve problems that the DC heroes can't solve with their usual methods.
He could be devastated. Edward is deeply in love with Bella, so he might go into a state of depression. He may isolate himself from his vampire family and friends, constantly replaying in his mind what went wrong in their relationship.
One reason could be exhaustion. Naruto has been through a lot in the original story. In a fanfic, if he is continuously put through more and more difficult situations without proper breaks, he might just give up out of sheer tiredness.
The story could take a dark turn. Without his heart, Naruto might become a soulless being, and his friends would be devastated. They might try to find a way to get his heart back. Maybe they search for a powerful sage or some ancient magic that could reverse what has been done.