Can the novel The Return of the Native written by Thomas Hardy be related as a piece of Realism or Romanticism?

Thomas Hardy is classified as neither a romantic nor a
realistic writer but a naturalistic one.  However, since naturalism is in many ways an
outgrowth of realism, Hardy probably aligns more closely to the realistic school than to
the romantic.  Naturalism is literary movement of the late nineteenth and
early twentieth century purporting that social conditions, heredity, and environment, in
other words harsh and uncaring nature, were the inescapable forces that shaped  human
circumstances and destiny.  In contrast, romantic writing usually includes more
idealism, symbolism and even reliance on the supernatural.  You are right that Hardy
does show some influence of the Romantics in his descriptions of the sweeping moors and
the powerful love, but ultimately his characters succumb to naturalistic forces and the
outcome of The Return of the Native, with Eustacia Vye caught in the vortex of the river
in a violent storm, is strongly naturalistic.  Interestingly, the positive
"Aftercourses" chapter was not Hardy's choice for the ending of his novel; it was
pressed upon him by his publisher in order to please the readers.  It has less of the
dark naturalism than the rest of the book.  It was insightful of you to notice the
romantic epigraph; you are right that Hardy shows influences of both schools, but
naturalism is clearly closer to realism than to romanticism.