I forgot, but I guess cos he was born or raised in America.
As cover for him keeping an eye on the red haired antagonist. Plus he has a name from his biological family and his other one from his adoptive parents.
In the korean ver his name isn't Gio it's dowoon(smth lik that) so when he was raised in America they gave him a foreign name which is Daniel and that makes sense BUT in the eng ver his name isnt korea to begin with that's why many of us were confused about him having two foreign names
Why does Gio have 2 names again?