I think Mon-El became aware of his romantic feelings when he and Kara were imprisoned at Cadmus together and she risked her life to save his. Maybe he found her attractive before, but at this point he got to experience her heroism and courage personally and right after that, asked Winn and Jimmy about if she was mated to anyone and about how mating customs worked on Earth.
To me, I think this indicates that his feelings are serious and his intentions are long term. While he may not know about all of Earth’s dating customs, he is usually pretty confident with girls. I don’t think he wants to just date or sleep with Kara; I think he thinks she is THE ONE. He wants to marry/mate with her for life. But he doesn’t think she feels the same way so he keeps it himself. And as he says later, he’s never felt this way about anyone else before and I don’t think he quite knows what to do. He’s terrified so he hides how he feels. I think he also thinks she has already made up her mind about him so he respects her enough not to put his feelings on her without some indication that she might feel the same.
At Thanksgiving, she becomes aware that he might be feeling something when Eliza tells her that he was being extra nice because he liked her. He made a super sweet toast to Kara, but still didn’t push his romantic feelings on her. I think this is when she started to reciprocate with her own feelings of attraction a little too but she wasn’t open to having a relationship yet so she wouldn’t have been open to receiving his affection anyway. (Side Note: I think Mon-El can read Kara way better than anyone gives him credit for but that’s a post for another day.)
Later when he was sick and they were playing Monopoly Kara asked him if he LIKED her and while he wouldn’t straight up lie, he dodged the question three times and three different ways to give the impression that he wasn’t interested. Why? He didn’t think she felt the same way and didn’t want to put himself out there or add pressure or weirdness to the situation.
It wasn’t until he was delirious with fever and thought he was going to die that he found the courage to kiss her… and he was super slow and obvious about it to make sure she was open to it. She knew what he was doing and could have dodged it if she wanted to and she didn’t. She kissed him back instead. But, when he was better again and she wanted to talk about it, he denied remembering it at all so that he didn’t have to own up to his feelings. You know he remembered because when she asked if they were going to talk about what happened between them he said, “Why, what did I do?” and when Kara didn’t tell him, they both pretended like it hadn’t happened because it was easier than facing that something was starting to develop between them.
When they start working together his little weakness started to show because he would make stupid decisions in the field in order to protect Kara instead of letting her hold her own ground - which resulted in her calling him out about kissing her when he was sick and asking him again if he liked her.
This is what finally gets him to confess. He is clearly so nervous about it and comes to her apartment tell her how he feels - because she asked that he tell her- and then he asks her if they can move forward as partners since he believes she doesn’t feel the same way. He high fives her and leaves her apartment with no expectations that she reciprocate his feelings or enter into a relationship with her after putting himself out there in an extremely vulnerable (and romantic) way. He just asks that they ignore it and move forward since he had been honest as she had asked.
And oh, the next part is so brutal. When she tells him in the bar that even if she had time to date she wouldn’t date him because of “the way that he is.” You can just hear his heart getting crushed all over the floor.. and then he just says “I’m going to go over there” in a complete panic flight move like he cannot handle being in the conversation any more because it is too painful. This is what he had been afraid of- what he had already felt deep down- that he wasn’t good enough for her and that she still couldn’t see past her first impression of him enough to give him a chance. This is part of why he didn’t tell her before- and when he confessed as she had asked, this is what he got in return. Ouch.
Kara didn’t mean to hurt him and she knew that her words came out wrong but it wasn’t until her conversation with Alex that she realized she did actually like him and wanted to give him a chance.
And by then he had moved onto Self Preservation Attempt #362 by asking Eve out - moving on with the girl who had been totally into him when he first arrived… and he can’t even make it work with her because he can’t shut up about Kara long enough for one lousy lunch date.
But in Self Preservation Attempt #363 he leads Kara to believe that he and Eve are still dating so that he doesn’t have to look like the pathetic rejected loser that he feels like inside. And this gives him the confidence to try to continue the friendship with Kara- to show up while she’s training with his confident exterior and basically call her out on avoiding him and say that he misses training with her. And when she first says she was mad because she thought he was dating Eve (revealing that she knew he really wasn’t) he completely lost his armor and got so vulnerable again and couldn’t look at her for a minute and it took him a good long while to get around to asking about why in the world she would be mad because he was too focused on the fact that she knew he couldn’t date anyone else because he was too hung up on her.
His face when Kara tells him that she doesn’t want to “woulda, coulda, shoulda” anymore is so priceless. He gets this little glimmer of hope and then as she keeps talking the glimmer gets bigger and bigger and then when she hits him with her comet eyes and says “Maybe I can have it all,” he is literally stunned speechless. And there is this moment where she finally FINALLY returns his feelings and wants to try a relationship with him, and she leans in to kiss him, and… Mr. Mxyzptlk shows up.
Mon-El acted pretty jealous and insecure with Mxy. Out of context of the rest of this romantic journey it seems completely over the top how he saw Mxy as a serious romantic threat while Kara and the audience just saw him as more of nuisance to get rid of. He also seemed threatened by how Mxy could give Kara anything she wanted at the snap of his fingers, which also seems a little over the top until you consider that he probably used to be that guy back on Daxam. Remember he told Kara he had taken a girl to the crystal planet once… he had the ability to give a girl anything or take her anywhere and impress her, and it always worked. And now he just has… himself. And he’s on pretty shaky ground regarding how Kara feels about him since she’s only barely told him she’s interested. And Mxy wants everything HE wants with Kara and puts her in a wedding dress and proposes with a big diamond on bended knee. Kara isn’t really impressed by those big displays and wants to get back to Mon-El instead but he can’t quite believe that yet and so he gets insanely jealous and tries to get rid of Mxy as fast as he can by challenging Mxy to a battle to the death for Kara’s hand - again a completely old fashioned approach that probably reflects how such things were handled on Daxam. Not only does he lose, but Kara is angry with him for getting involved and tells him AGAIN that it’s not going to work out between them. And he is crushed yet again but apologizes and respects her wishes and leaves so that she can go marry Mxy.
Post-Mxy, he comes back to her apartment only to apologize and tell her she’s awesome, but with no expectation of anything romantic happening between them. He says he’s sorry, that he was out of line and tries to leave. Kara stops him by moving RIGHT in front of him and flashes him the comet eyes again, and you can just see him trying to figure it out WHAT is going on because her body language is saying “take me now” but didn’t she just break up with him? So he takes a big breath and tries to tell her how he is listening to her and respects that she doesn’t think they belong together… until she says that she tricked him too and she really does want him after all. This poor guy. Seriously. And he keeps clarifying and clarifying until he is absolutely certain of what she wants. And only then does he kiss her and she kisses him back with equal passion and urgency, and they both finally just let go of their fears and tumble down this rabbit hole together.
If I’ll write a Lunyx long fic … In more episodes… Sort of following the canon plot but also not … Where Nyx survives and try to “see Luna safe to Altissia” … With all the stuff we see Luna doing in the canon game too, but with Nyx … Would you guys read it?
That would include:
Nyx and Luna changing their clothes somewhere, meeting Umbra/Gentiana out of Insomnia, Luna going to Titan, the actual journey, then Luna speaking with Ramuh, Nyx protecting her all along, Luna healing people with Nyx watching her back, Nyx having back his magic thanks to Noctis becoming the new source of lucian powers, Nyx and Luna in Tenabrae, Nyx seeing her wedding dress designed for her wedding with Noctis, angst, Ravus meeting Nyx in Tenabrae, Ravus yelling at Luna because of her mission, Nyx asking about “what mission”, Nyx feeling betrayed by Luna, Nyx descovering that Luna’s mission is so dangerous she’s probably gonna die, Nyx promising to Ravus that Luna won’t die, angst again, their journey to Altissia, Luna’s affection for Noctis, Altissia! Gondalas, restaurants, sunsets and hotels, maybe a stolen kiss on the gondola, then the Leviatan mess and only god knows what else and how all this could end …