Somebody

I'm on Chapter 8, and I have a question why is the MC such a busybody and so glued to a random girl he just met on the street?

So, I watched the anime, and after the Queen Mother’s rebellion, I have mixed feelings about this series. I mean, why the fuck didn’t Sei kill her? How is that even possible? They portrayed Sei as a benevolent king who cares about his people, someone who’s different. But here we have the Queen Mother killing thousands of innocent people in a rebellion that she was the primary cause of. Didn’t those innocent soldiers and citizens who died in that battle have families too?!
Just because she’s his mother, he feels sympathy for her and doesn’t kill her. That makes him no different from other kings. I really liked this series, and even now I’m here reading it after the end of the anime, but this topic still makes me unable to enjoy it like I used to.
So does anyone know why he did this? I mean, she even had children with another man. I think in that period that was a huge taboo. How the hell did he forgive her and even promise to bring her children back to her? It’s like those innocent people who died aren’t worth his mother’s life. For fuck’s sake, even his wife and children were near death. How could he spare this bitch? Had the rebellion succeeded, everything he cared for would have been destroyed—his goals, his friends, his family. He would have lost everything, and I doubt the Queen Mother would have shown him any mercy.