Actually, this is the second time she was shown with her hair down. She looks surprisingly young (and beautiful).
Looking at the painting reminds me of Emperor Ai, since "cut sleeve" is usually refer to him.
Except the manga is romanticizing cheating. The main couple Michi and Makoto had affairs with each other despite them being married to another. Instead of calling them out for cheating on their spouses, their affairs are romanticized and celebrated by the authors and the readers, even though...
Just because the manga started in 2017 doesn't mean the author couldn't include that. The chapter part of the novel could have written after the research result was announced.
...again? Why is there a continuation? The story ended up on a good note, and they just had to continue it with the boring "broken engagement" plot.
And how is the marriage between the king and the queen loveless anyway? It may not be romantic, but their relationship is the best and long-lasting.
There is nothing mature about a woman who chose to have an affair with a married man instead of divorcing her husband first. Make up excuses all you want, but that is just selfishness. She deserved to be blamed as well since she destroyed the man's marriage by seducing him.