Harry died during the Battle of Hogwarts, but his sacrifice allowed everyone else to take down Voldemort. Yet the troubles only began there. There was no prominent figure to rally around, and so what was left of the Order and the DA were unable to take on the Ministry, who was slowly taken over by the "neutral" purebloods, who removed the worst of Voldemort, but kept many of the smaller, economic and social laws and regulations, since they were quite comfortable for those in power.
With their position secured, the British elite turned to expanding their influence abroad, mostly by causing incidents, supplying arms, inciting revolts and such. Everything you'd need for a good proxy war. But they are clever about it, with very little you can actually prove and link back to magical Britain. And smelling weakness, the magical French Empire and the Holy/Magical Roman Empire decide that they want a slice of that pie as well and add more fuel into the fire. Not big wars, but proxy conflicts.
So with Europe descending further and further into chaos and many still suffering from the war with Voldemort, Britain isn't a great place to be. Neither is the rest of Europe. But Fleur isn't having any of this, she has build a life for herself, and even though her marriage hasn't worked out, she has a daughter and for Victorie, she'd do anything. Including turning to Necromancy. And stealing a body from a mausoleum.
After all, Harry had taken care of Voldemort, so he could fix things again. Raising the dead is easy, but she does not need a mindless drone, she needs Harry the way he defeated Voldemort. For two years, she reads every book she can find, restoring what Voldemort and time had destroyed. Magical cloning, a touch of magical cybernetics and such.So when Harry wakes up, he's pretty pissed. He remembered taking on Voldemort, then the Kings Cross scene, and despite moving on he was back in England, and things were shit again. Only Fleur's tale of how awful the world has become, how badly his friends had fared, stop him from getting up and leaving. So they come up with a plan, but they clash about methods, plans and everything in between. They only share a common goal.
Harry also feels a massive disconnect since he has been dead for almost a decade apparently. He is supposed to stay hidden, but feels lonely and tries to get in touch with his friends. Hermione is in Australia, but he finds Ron, who does not belive Harry at all. After all, Ron had been at the funeral.
The overall outline would be Harry and Fleur learning to work together, Harry dealing with his existential crisis and them slowly catching feelings while slowly trying to fix the dumpster fire magical Europe has become, first by intervening in proxy wars to spoil plans and later on taking on the leaderships of the big 3 (UK, France, HRE)