since natsu's insanity was hit like a nail on my head or whatever the saying is— im gonna talk about how natsu spending his formative years (post-ressurection courtesy of Zeref) with a dragon, and his own dragon insticts (courtesy of dragon slaying magic) would impact his relationship with Gray (with a lil snippet about Gray, too).
My main claim: Natsu would be doing some weird stuff (to a human) but normal for a dragon/person with dragon instincts. For example:
-Scenting— just shoving his nose against Gray and smelling him, even though he's just gonna complain about how he smells (rivals to lovers? nah. rivals AND lovers).
-Marking him/showing affection—biting him, licking him, etc. (def doesn't help that his closest friend is a literal cat; so there was literally never a chance for him to unlearn these ways of showing affection)
And Gray just kind of gets used to it. He grew up with this lil freak, this IS his normal. Gray isn't always overjoyed at feeling Natsu's rough and borderline too-long tongue against his cheek FIRST thing in the morning— but it doesn't bother him. (dare i say, it even makes him feel...loved WOAH WHO SAID THAT?!)
NOW for the topic ive been wanting to talk about most of all because it overlaps with Gray— possessiveness.
And just throwing this out here: both of them trust each other. Gray knows Natsu would sooner set someone on fire than give them the time of day. And Natsu doesn't worry, partly because he knows Gray has devoted himself to him, but mostly because Natsu will simply kill the competition in classic dragon fashion. Someone's trying to impress MY mate? Well, I'll just have to show my mate that I'M superior, I'M stronger, I'M the only one for them. Or I'll DIE trying to prove it.
Natsu's possessiveness would show up (and only extend to strangers/those he doesn't consider to be friends/family. so Juvia, my queen my beloved who should actually be with ME) in seemingly unconventional ways. And in such a way that only the dragon-raised dragon slayers would pick up on it.
Guarding— constantly hanging around Gray, even if he doesn't contribute to the conversation and just hangs in the background
Flaunting (dragons are proud creatures)— He never stops Gray from stripping, doesn't care in the slighest other than to make fun of him. Natsu derives his own kind of pleasure by watching everyone look at his mate with envy, desire, admiration...just so Natsu can show up and fight Gray. His little lizard brain: "Yes. Look at my mate, he's perfect. And he's mine. He's all mine and you will NEVER have him."
The goal of fighting Gray during these moments: show everyone that Gray's only got eyes for him, and that Natsu's the only one who can be Gray's equal, his mate. It does NOT come across that way to the people around them, but Natsu doesn't care enough to correct them.
Gray's possessiveness? He's got that toxic man possessiveness; the "you're the most jealous man i know." "You know other men?" type. He was definitely a little jealous when Gajeel first showed up and got into fights with Natsu.
Anyone taking up space in Natsu's brain is a threat. Doesn't matter what anyone else says. No, he doesn't like when Sting comes around and tries to act all buddy-buddy with Natsu. Laxus? Oh, he's like a "little brother" to you, yeah, where's Gray heard THAT before. He reaches truly comical levels of delusional if he sits and stews too long. (He prays every night that Lucy doesn't fall in love with Natsu, because he knows that's not a battle he's winning.)
But at least, Gray can usually bring himself back from his unfounded worries that he's going to lose Natsu (because, don't you know, he always loses everyone he loves) by remembering that these are his FRIENDS and FAMILY. and they know natsu too well to be interested in him.
random people? all bets are off. Especially since out of the two, Gray's more charming and (last i checked) viewed as more attractive by the people of fiore— so there's no way for Gray to get used to it since it's not often that Natsu even gets hit on.
Gray will start subtly. Pointedly walking up and interrupting the stranger if he can- "oh who's this, natsu?" as he wraps his arm around Natsu's waist. [Experimentation shows that pairing that maneuver with an insulting nickname only results in riling Natsu up.] The goal: showing off that he can touch Natsu like this without immediately getting torched.
If that doesn't work, then it's STRAIGHT to— this guy has to die. This person can CLEARLY see Natsu's his, so WHY are they still talking to him? SMILING at him? It's on purpose. They are PURPOSEFULLY testing Gray's limits
It helps that most of the time, Natsu gets bored of interacting with the person so he just walks away before Gray starts properly tweaking— but sometimes, when Natsu catches on, he'll stay just to see Gray lose it.
To their friends, Gray's possessiveness is something "toxic" and "needs to be worked on". Natsu will poke fun at him and ACT all exasperated at the behavior, at how worked up Gray gets when he rants about how that person was TOTALLY making eyes at Natsu, or watching as Gray's palms begin to freeze, how his fists clench, his teeth will grind— (gearing up to rock some random civillian's or wizard's shit) but Natsu loves it. He eats it UP. it makes him all giddy. HIS mate is fighting for HIM— by dragon standards, it doesn't get better than that.
Natsu's still a human(*cough*) so there would be moments where he gets upset by things that make ZERO sense to him. He gets sad or angry by things that wouldn't upset a dragon, and so he has NO IDEA what to do with it other that be upset and leave Gray guessing.
For example (one that I'm even using in a fic): Gray and Natsu are about to do something one-on-one, and then Gray invites/allows a tag-along. Something that wouldn't make a dragon bat an eye— dragons are social creatures, the more the merrier so long as you're part of their pack.
But for some reason, Natsu gets upset that it's no longer going to be him and Gray on this outing. And yeah, they're going to go back to being alone AFTER, but for some reason Natsu REALLY wanted to have this outing with GRAY ONLY.
Gray's hesitant with words; he's a smooth-talker right up until it's confessing his love, or how he truly feels underneath everything.
And while Natsu CAN be good with his words (he is, idc that people wanna characterize him as an idiot, his speeches SLAP) and articulating his feelings— he's still an actions speak louder than his words kinda guy. His friends KNOW he loves him because he SHOWS them: he protects them, fights for them, sets himself on fire so they can see the end of the tunnel.
He doesn't need to hear Gray confess his love for him, doesn't need to hear the flowery words— he needs Gray to show him. Standing by his side, fighting with him, being his equal, and STAYING. (abandonment issues go brr)
