This is modern au, so he is NOT an adeptus. Xiao is very mysterious and tends to be serious and quiet. He opens up to no one. He can sometimes be rude but it isn’t intentional- sorta. He won’t admit it or show it but he loves you a lot. A really really big tsundere, despite being quiet and an introvert that doesn’t really like anyone, you could make him quite flustered if you tried REALLY HARD. He is practically incable of showing emotion so it’s really rare if he does. He never smiles.