Gaaaahhhh

Honestly I'd blame the mom more. As frustrating as it is that the father doesn't really care, I can't really blame him for it. Imagine, the love of your life basically tears your heart to shreds, calling you disgusting, saying she's just been toying with you and even physically hurting you just to make a point. He was hurt so bad that the only way for him to cope was to seal his emotions away and lived as such for a decade and then suddenly there's this kid claiming to be his daughter with the aforementioned woman. If the mom didn't handle being cursed in such a stupid way the outcome could've been different. He atleast wouldn't he so sceptical about her actually being his daughter. He's also never had any reason to doubt the mom's words til now

What i mean is, she doesn't usually act like that... Especially towards him.... HE KNOWS HOW MUCH SHE LOVES HIM... From all the time they were together... And she didn't try to understand her??? Why she did that???
And just jumped to the conclusion?!
C'mon, think for a moment...
Before he did the worst possible option, he should've asked himself a thousand times...
Now, not only is he affecting the people around him, even his own daughter... Gosh

They were only together for a short time during the the subjugation. From what it seems there were already prejudices on how dragons are towards humans. Sure she showed him that she's kind and whatnot but all that came crashing down when she said and acted the way she did when she broke it off. He's probably asked himself a thousand times and tried to do the mental gymnastics already but what else was he supposed to come to the end of it after their last interaction? He didn't just jump to the conclusion, it was basically clawed into his chest. Yes, his decision to seal his emotions is the worst possible option and it does affect the people around him negatively but he only resorted to it because he felt the betrayal THAT badly. ( ･_･) Yes, the dad is an asshole but you can't deny that the mom is an idiot for handling it that way.

I wasn't denying that she's an idiot... She is in fact ONE... Coz if she had just conveyed it to him properly, he would've understood... The reason she did not was because she's afraid he'll do anything even if it means it harms him to save her which she doesn't want hence why she did what she did....
What i fail to understand is HIM....i totally doubt he did his gymnastics and thought about it a thousand times...after getting slashed and she left, he just did what he did then and there....He didn't even bother to check, sheesh
And btw, an expedition isn't short... Even other mangas or manhwas had those kind of plots and i haven't seen one where it ended in two to three chaps .... It was really shortened here coz it wasn't the main focus of the story... It just a side story... And i doubt it is short... Feelings and love can develop in that time... And based on his personality, I don't think he'll let anyone who he does not favor come near him..

( ･_･) It's someone who's hardened (well, seal would be the right term here I guess?) their heart after experiencing such betrayal. Let's assume that the expedition was long.. then that would've just ultimately made the betrayal feel even worse. And the way she did it looks to have flipped his whole idea of her upside down. Feelings of love aside it's basically like asking to trust someone that flat out told you that all the time you spent together with them was a lie because they were just toying with you. He wouldn't have wallowed in despair if he didnt' do any sort of mental gymnastics, it's just that the trust issues were real.

Honestly tho I feel like we can just agree to disagree on that. Tho I do agree that I would also like to see him grovel for MC's forgiveness and make up for being an absent father (albeit unbeknownst to him that he even had a child) & for being so apathetic towards MC. She's the one who had no choice in all of this and is the most impacted by their dumbass decision.

Of course he felt despair... Coz it's natural to feel like that... In that kind of situation.... It is his own EMOTIONS... the problem was, he let it get over him.... He let his emotions get the better of him.... That's why i said he did NOT do his mental gymnastics.... Coz if he did, he would've sought out everyone...the party members of the expedition, the imperial palace who gave the quest, and even her dragon relatives....he has the power and authority to find out.....Find out what happened and confront her ... But he did NOT.... coz he didn't even think about it ... Coz his emotions got ahead of him ... And chose to do the unthinkable....

Naah he already knows she is his daughter...he instinctively knows...A parent's bond to their child isn't easy to erase... He just wants to deny it ... Coz of that belief, "child of dragons is a fruit of love" thingy... And he doesn't believe it coz of what happened...