
At first I was slightly confused, then bewildered, then enraged (by Luca's apparent heartlessness and Setsu's hopeless pursuit), then understood things turned out for the best (of Luca's interest, and perhaps, Setsu's and Saki's too).
Had Luca been healthy, things would not unfold the way they were.
When people know they're about to die, they do reckless things - things that are beyond ever imaginable to them.
Thanks to Luca's vision and determination (or, borderline heartlessness), and also the hand of fate, Setsu is left in the good care of Saki (or vice versa, for that matter) - a man who received Luca's approval enough that he was allowed to sit in his throne.
The sick man left the world in defense of his family's honour - he who, even if defeated, died a glorious death, his illness unknown to anyone besides his closest aide. The love of his life has been taken care of (or vice versa) by the best friend he understood and trusted most.
With the illness, win-win.
Without the illness, happiness for everyone (Luca, Setsu, Saki - though with someone else).
I remember seeing an anime scene similar to the part where the guy recorded audios of confessions..
I’m not sure if this happened in the anime but it seems like something the male lead from “wolf girl and black prince” would do