I’m forever a fan of weird Galra traits manifesting in Keith so consider — when Shiro gets back from Kerberos & he’s just ABSOLUTE BEEF, Keith is having a crisis bc his Galra lizard brain is like BIG STRONG MATE BIG & he FIXATES & shiro notices....

Galra Brain also goes wild for Shiro’s scars bc the logic is that the more scars you have, the better you are at fighting/surviving so the first time Keith sees them he’s struck with the overwhelming urge to get his mouth on all of them & leave marks of his own bc Shiro is HIS

& as the Galran hormones start kickin off w the catalyst of Shiro Big, Keith starts growing and more Galra traits start coming up - he gets hyper-attuned and attached to Shiro’s scent, he can’t sleep well alone when Shiro is in the next room, his fangs come out whenever they spar

Keith definitely gets kind of nasty w it too and he doesn’t know WHY he’s doing it but he knows he needs to - he finds himself stealing Shiro’s dirty underwear/undershirts bc he NEEDS the smell; & whenever aliens approach Shiro with ~interest~ Keith can get downright VICIOUS

And THEN oh boy when Keith’s first Galra mating cycle starts it’s just a MESS - i like the hc that Galra are intersex so it’s less heat/rut and more like IT IS TIME TO FUCK. but Keith doesn’t know what’s happening!! all he knows is that he can’t let Shiro out of his sight!!!

& it’s SO MUCH that it’s almost kinda creepy & neither of them know Keith is Galra yet, but he just fuckin shows up in the middle of the night in Shiro’s doorway w his glowing cat eyes like “Shiro I’m here don’t worry” & Shiro is like “KEITH I’M A LITTLE WORRIED!!!”

Keith goes to his bed & stands over him & says “I’m not going to let anyone hurt you again” & Shiro is like ???? & Keith just sorta flops down onto his bed with him & lays his hand on Shiro’s chest over his heartbeat & says, “I won’t let them touch you” & Shiro is like “oh.”

So Shiro figures out he’s Galra first when Keith falls asleep snuggled against him & his nails shift into claws in his sleep & he starts purring. Shiro has kind of a crisis, panics, gets out of bed to talk himself down in the bathroom & remember how to breathe; bc it’s just KEITH

So Shiro persuades himself it’s fine, they can get through this, and is debating telling Keith, but when he gets back into the bedroom Keith is awake and inconsolable; he freaks out when he sees Shiro & tackles him onto the bed & won’t let go bc he’s terrified he’ll leave again

Because something that neither Shiro nor Keith know is that sometimes, Galra imprint on a single mate pretty much as soon as they hit sexual maturity, & Keith did that with Shiro right before Shiro left for Kerberos, so when the bond was at its most vulnerable it got shattered

And the damaged imprint turned Keith into this half feral creature during the mating cycle when the bond is overwhelming, but ofc humans...don’t imprint. So Shiro doesn’t know what’s going on with him, & it breaks his heart to see Keith so distressed & sure Shiro will abandon him

And, as much as Shiro tells himself it’s Keith & it’s fine, something in him panics at being pinned down by a Galra; his arm activates & Keith just freaks out more bc he doesn’t understand why his mate is fighting him!! Why doesn’t he want Keith; why isn’t Keith good enough??

Shiro tries to leave the room & Keith almost gets violent; tries to restrain him so he won’t go & he manages to do so with horny sad Galra strength, but as soon as he realizes Shiro is afraid & anxious Keith shuts down & lets go ;-; When Shiro leaves for help, Keith just gives up

So Shiro comes back with Allura to see what’s wrong and they find Keith just crumpled in the corner crying, & he looks up at Shiro with huge eyes like “I’m sorry I don’t know what’s wrong with me” & humans don’t imprint but Shiro swears to never ever let Keith go right then

And this comes up later in the Blade trials when Shiro is like GET HIM OUT & Kolivan snaps that he has no right to care about Keith when he’s the reason Keith has such a fucked up mating bond, bc he left Keith behind on Earth...& maybe humans can’t imprint, but Shiro gets PISSED

Shiro is like how dare you assume to know ANYTHING about what I feel for Keith & how much he means to me I don’t CARE about mystical mating bonds he’s my best friend & thinking about returning to him KEPT ME ALIVE as the champion so you can take your imprint shit & shove it!!!!!!

& Kolivan kinda backs off & is like ok fine he may be your best friend but you can’t be his mate, we’re his family & his kind & what he needs, & Kolivan points to Keith’s hallucinations as proof like “look, he’s so scared you’ll abandon him, and with good reason!”

& Shiro barely stops himself from punching the leader of the Blades in the nose before storming down to get Keith himself; he has to go through five blades to do so & he doesn’t care, actually - Keith is what matters & Shiro can’t stand seeing him in pain

When he gets to Keith, Keith just crumples into his arms & keeps mumbling “I’m sorry, I’m sorry,” & Shiro doesn’t know what to do but he remembers smth from the Galran ships & tucks Keith close to him, Keith’s face pressed to his throat, & Keith whimpers & folds into him