The elves integrated into the human empire without major issues. There were issues here and there, mainly cultural.
The elves were stupefied by the attention they suddenly got. Humans started building fan clubs, cheer groups, and more. They felt like objects in the zoo and that was the biggest challenge they faced.
Thankfully, after some cultural exchanges organized by the imperial media, people treated them as another sub-group within the larger family.
The common people had no idea that these beautiful, slender, and seemingly peace-loving elves were in fact pretty combative and had six whole celestial rankers.
But from the friendly duels, the military concluded their own assessments of the elves.
These elves had no problem sacrificing their own for a victory in a duel. They hated losing. But even more worrying, they'd pay any price to come out on top—even sacrificing their own teammates.