Integration
Angels have been on the Surface for as long as any living human can remember. Generations grow up sharing classrooms with little feathered children before those are asked to join in service of the Council at 13. Up until they reach that age angels and human children are considered the same, allowed a cheerful and innocent childhood. After that things change. The angel children start visiting the Council building and learning how to utilize their natural talents to protect the human race. Ultimately, they learn how to kill.
And while this is considered a noble task by most, both angels and humans, some realize that the ones killed are not just demons. That they used to be humans themselves.
Inevitably that leads to some level of weariness in most humans. After all, could you easily share an office desk with a professional killer?
Saying that, many angels still manage to lead a normal human live and blend in. Winged or flying creatures have long stopped to surprise humanity and a lot of mixed marriages occur as long as the human party agrees to let their spouse do their other job while on the way to pick the kids up from school.