Essentially the female and male protagonists met when they were both a child and during a war-torned town. He took her in, taught her swordsmanship, gave her food, shelter and possibly proper education. This guy was everything to her. She fell in love, confessed, but was rejected. Okay.
From what I could gather, the reason behind the rejection is, well, pretty generic. If he felt and allowed himself to love, he thought his whole plan of taking the kingdom over and becoming the ruler would be ruined, because as many times have showed, dirty and immoral tactics is his best friend.
Okay, fair enough?
Speaking of dirty and immoral tactics, other than rejecting the female lead's confession, he sold her. Yep, that's right. He sold her, a CHILD, let me yell it louder for the back, a MERE CHILD, to some rich lady, knowing very clearly one of her pastimes (she said it herself) was abusing her workers. What did the male lead get in return from this dark, dark transaction? A castle.
In summary, the male lead sold a child to a aristocratic lady to be whipped and abused daily. Treated worse than a slave doing hard labor. Keep in mind, the female lead loves holding the sword and fighting. It gave her, a woman living in a hard era, freedom. So, her pride as a woman and a 'soldier' was also stripped. He gave her everything , took them aaaalll away, and more. How would you even feel?
Years later, they met in the most cruel way possible. Dressed in a tight and big puffy gown, she was immediately summoned to the palace by the male lead (current ruler), because he was trying to find her the whole time. Oh, but he doesn't recognize her at first. After being treated like some prostitute during their first night, it was revealed her body was covered with old scars. (Her identity was not known to him at the time, but is it me or is it very odd how the first thing you would do to someone you've treated so terribly wrong for years is to sleep with her? Keep in mind, it's either the female lead sleeping with the ruler, or being surrounded by soldiers and killed.)
Anywho, to him he might've done a heroic job, but to her it was the most mockery she could've ever received- her wounds, that were received from years of torture because of him, were healed by magic in a blink from the best doctors he forcibly ordered to.
Chapters later, he then finds out her true identity.
So, as the manhwa furthers in, it's mostly him begging for her forgiveness, as what's most important is him wanting to feel right and be a good person, instead of trying to understand that sometimes in life, one's actions can be so atrocious that it doesn't have to be forgiven? That, maybe instead of shoving your face and telling her how important it is for you to be forgiven and feel right, what the best course of action you should've took was give her a place to live, far, far away from the man she once loved and trusted deeply. By Gods, logically from such an experience one would throw up just thinking of him from all the PTSD and trauma.
To make matters worse, he didn't tell a single friend of his what actually happened. All the soldiers and people that currently work for him, only knows his version of the story, and that is some form of tragedy struck and the female lead was killed in a battle. And, now, the reason why these people care for the female lead is because some of the people that works for the male lead are also the same people that were in the mercenary group both female and male lead were in. They have years of friendship and brotherhood with the female lead. They care. Only was he in a drunken state, did he pathetically revealed the truth to one of his comrade. The maid that was working under the aristocratic lady's house, one of the few people that protected the female lead and brought her food? After being pushed to the floor and interrogated by the male lead (years after the female lead escaped, IIRC), she was KILLED. Because she spoke the truth, something the male lead did not like. Instead of kissing her feet and thanking her a million times for having the courage to protect a MERE CHILD from being abused, that's what the maid got.
This story tries to throw in a male lead with a plot twist. I don't think they're deemed to be bad from the getgo, because it can be a challenge for the author to try and write a 'redeeming' arc for him, and if it's written well, it's done well. Not this case.
As the reader, and with stories like these that are specifically written for the female audience, we're supposed to be happy for the female and male lead.
But, hey, at least one thing was written right. The male lead is actually a tyrant by the definition, instead of "He's a tyrannical king, but actually he's just a coldhearted and misunderstood person that has a heart of gold and loves his people but he only evvvverrr smiles to the female lead and has a 12 pack and body shaped like an upside-down triangleee omg simp daddy".