one of us

a person recognized as an accepted member of a particular group, typically one that is exclusive in some way

自己人

us and them (or them and us)

expressing a sense of division within a group of people

我们和他们，自己人和非自己人

negotiations were hampered by an ‘us and them’ attitude between management and unions.

劳资谈判因对立态度受阻。