Can Diana fight? (I don't think she can)

I am not so sure about that, like I get that Heli is not expecting much from Diana but it also didn't take Heli long to you know sort start emotionally cheat on Diana. I am definitely not gonna like a guy who starts looking at other women and relationships as soon as his own become less than ideal or even a couple of weeks of fight. Hestia definitely doesn't like Heli but Heli himself is starting to tow the lines now with his completely onesided feelings, his feelings might be slightly ambiguous about whether he actually likes Hestia or likes what she provides in a relationship but the lines are certainly blurry. Of course Diana also has her own issues and is starting to have her own slight (for now) cheating adventures. They look like a pair who jumped into a relationship they were unprepared for and are basically both starting to cheat in some measures after just some disappointment in their relationship. And no matter how rich a guy is nobody will tolerate a cheater.

Heli and Diana are unprepared for an actual relationship alright lol

Actually, Heli expected A LOT from Diana. In fact, she expected her to rule WITH him. To help him w governing and such. (Pretty funny how he's expecting such actions from a commoner who is not trained and not... capable like Diana. But oh well.)

Heli is actually hella responsible when it comes to his official duties. In fact, I whole heartedly think he did love Diana until the very end of the novel. BUT fcking Diana is inflexible, a big liability and so incapable to lead that he decided to choose his work than love.

Thats also WHY he kinda had a bit of crush towards Hes at one point. It's just a short lived crush guys lol you all it's not like it was love or smth. What he liked is how capable Hes is when it comes to her duties. Her skill is what Heli likes about her (at least thats the main reaosn imo)

Last one, I was just being silly when I said I'll fight Diana for Heli jeez I'm not serious!

No, I get what you mean, Diana is definitely unprepared for the role she has and Heli hasn't really helped her get the education she needs for this role either (also Diana has a habit of burning bridges with people that can actually help her with this role like the head maid of Palace so it's definitely a problem contributed by both sides), what Heli is asking may not seem much to most modern audiences with education but is definitely a lot for any uneducated women who is suddenly thrown in a different class situation and dynamics. I just wanted to point out how rushed their relationship actually is that they can't even deal with the very first big fight.

As for Heli's slight crush on Hestia, it remains to be seen how it increases or decreases with time because the manhwa is changing things subtly from the novel as said by one of the commentors below, Kael himself seems are lot more mentally stable now compared to his Novel counter point. According to the novel spoilers that I have seen Heli's affection for Hestia were supposed to be somewhat like sibling affections but the manhwa is definitely hinting at something different, though the situation is still very ambiguous and can change at any time.

Also I completely get the joke, I just wanted to add my own cents in the discussion really.

And I agree w you somehow about both Heli and Diana not being ready to commit. The first sight of a disagreement and their relationship started to crumble lol

I read the novel many times and I never interpreted Heli's sudden attention to Hes as somewhat platonic. To me it's definitely more than platonic. There's attraction there for sure but not to the point of 'love' (like I said). Crush is the best way to describe it imo, a crush that stems from his admiration towards a strong willed woman like Hes (honestly, same. Kael and Heli def get it.)