
Oh sorry, the spoilers I read were here in the comments section. You can find them a few pages back.
Nvm I found a link to one of the major spoilers. http://www.mangago.zone/home/mangatopic/6856816/

Less spoilery poiler
....(scroll down)
MC main goal was to get close to ML and avoid cruelly killed by ML. But, after the chambermaid girl died.. he started to take his role as a north emperor seriously. He wanted to protect the people of his country.
He also realized that he and ML have to ended up in opposing sides. So he helped ML to get back to the southern kingdom.
MC actually ruled his kingdom well. But no matter what great things he have done.. there are somethings that cannot be changed. Which is the fact that southern kingdom will conquer the northern kingdom (and several other kingdoms), and ML will be the emperor who unify the land.
This is what makes it heartbreaking. MC done great things for his people but disasters keep happening one after another. And if MC succeeded in saving this person, that other person will ended up dead instead.
Don't worry MC and ML will have their happy ending! But the path to happy ending won't be easy.
I actually like that it's not easy for MC to change his caharcter's fate just because he have known the original novel story. Also it's interesting to notice what things changed and what things stays the same.
This story is becoming so depressing. I've already read some spoilers which had me not even wanting to read the novel because it's just so damn sad.