When Hestia was explaining, or Hesplaining to Kael her theory of why he no longer has feelings for Diana, being that he loved her so much that he let her go. You saw that look on Kael's face after? That was a look of a man completely defeated. He's tired of explaining to her that he doesn't like what's her face. The man was resigned. "Well. Hestia will be hestia. Just let her have this."
Also, anyone remembers the reason Hes died before her regression? Was she sick? Was it suicide? Why does she not believe she'll make it past this year?