Complex sentence: Thus Ishiguro ends many of his novels on a note of melancholic resignation, whereby his characters accept their past and who they have become, and find comfort in that realization by a relief from mental anguish.
Split into simpler sentences: Thus Ishiguro ends many of his novels on a note of melancholic resignation. His characters accept their past and who they have become, and find that this realization brings comfort and surcease from mental anguish.