So, the ending totally confirmed Dr. Choi and Se-ok are the same, and they really see through each other. She was spot-on about Dr. Choi wanting to off his friend. The only difference is Se-ok's impulsive, while Dr. Choi's way more strategic.
I'm so glad you're loving this drama! If they'd dropped all eight episodes at once, I would've binged it in a day – just like I did with Karma. I usually don't binge dramas.