The planet was heavily populated by no less than four extant sentient species, when the Evisceroids first perceived its existence. Genetic variety was heavy among two of the species that had spread to adapt to multiple extreme environments, which attracted the Empress. However, one of the remaining species was enjoying an industrial revolution that was removing that species' longetivity and appeal as they relied more on technology and pollution ran rampant. The last species was numerous but genetically 'bland'.
It required a bit of coordination between the Empress's chosen hivebrooder daughters to obtain as much genetic variety as possible on this new world. Among the eleven of them, a great competition arose, as whoever would provide the Empress with the greatest boon of this world, would likely receive the right to rule over the rest. And the rest would be reduced to the role of servants to the new Empress, discharged of their hivebrooder abilities and potential. A forced chemical metamorphosis into servitude for the rest of their lives.
But three of them decided that rather than compete fruitlessly against their stronger, more able sisters, they would attempt to find a new world for absorbing into the Evisceroid fold.
And find a new one, they did.
They invaded with small reconnaissance forces. And they found such variety. A world of great variety. Mammals, reptiles, avians, amphibians, arachnids, insects, piscines.
And each of the three Evisceroid hivebrooders took males to mate.
From those encounters, their hives began to bloom. And spread. And gain the attention of the world's concerned parties. Governments and police forces and armies got involved. Evisceroids were captured. Evisceroids were killed. Evisceroids were eliminated.
The young hivebrooder remembered the night the sky was lit on fire, as fighter jets roared overhead and delivered firebombs onto her home. She felt the air burn in her lungs as her children, her siblings, her family died all around her. She heard their screeches of pain, smelled their charred flesh.
Next to her was a slashling soldier and a worker drone by name. Doing their damnedest to remain by their mother, the only surviving hivebrooder, to the bitter end. Ready to start a new hive somewhere else, as needed.
"No."
The underlings turned to their superior in confusion. Never protesting, but certainly feeling conflicted.
"I know, you are receiving an order that counters all instinct within you. But we cannot be here. We cannot thrive on this world. The inhabitants are too powerful. We are too few. And we cannot grow from within, here."
The pheromone responses relayed their concern. A repetition of the last orders they had received from the elder hivebrooders. Spread and conquer as we always do.
The hivebrooder shook her head. "Go with your brothers. See to their safety, if you can. But I cannot stay here. I cannot be captured. I shall wander and hide. I shall wait until our Empress arrives."
The drone chirruped with a dejected sound. The inferior breeds within the Evisceroid hierarchy could not speak, but their olfactory and vibration-sensing faculties were enough to transmit the messages they required. Vocalizations, they learned on this world, influence tone and intent, or feeling, in their responses. But even with this evolution, the drone was only able to respond one way.
"I obey your command."
The slashling looked up at the hivebrooder, visibly struggling to accept the command and protest it at the same time.
She nodded her head slowly. "I understand your reluctance. I too am struggling with the realization. My role in the hive, as breeder, puts more in danger. And my instincts sometimes conflict with the best chances our race has for survivability."
She looked at her two inferiors, who looked up at her with blank expressions.
"... No, I do not suppose either of you would understand."
With a light chemical expulsion, she opened her arms to them. "Come hither. This may very well be my final gift to you. Use this to protect your brethren, and any who survive from our swarm."
The two servants approached the hivebrooder's chest. Her breasts held not milk, but a complex concoction of mutagens and proteins they refer to as 'royal jelly'. Their consumption was limited to special individuals and breeds, such as other hivebrooders, or to influence a mutation or adaptation in any of the subservient breeds such as those before them. They brought their mandibles to her breasts, and started licking and latching onto the teats, coaxing out some jelly for themselves.
The hivebrooder used her two lower arms to cradle their heads from underneath, and the upper arms to caress their heads from above, stroking them lovingly, with an ache in her heart. She had already witnessed the births and deaths of thousands of her own children, but somehow this parting felt meaningful.
Once they had had a fill, as they licked their lips, the hivebrooder used her lower hands to cover her breasts, massaging them gently, as she raised an upper hand to issue an order. The last order.
"Go."

She sighed as she returned to the present. From that moment until this, she had only felt tears streaking down her cheek twice. Once while she saw the shapes of her last two sons walking away, following her last order... and now, as she recalled the memory and vocalized it to Casey.
"From that moment until this, my travels and hiding have showed me that my kind, as we are right now, is dangerous. As strong as has been my instincts to start a new hive, I fear it wold only end in further destruction."
Casey sat wide-eyed at the creature before him, surprised at what had been told to him. Well, not so much surprised that governments did not want an alien invasion on their world, so they did everything possible to destroy the hives where they were found. And then covering everything up to prevent people from seeking them out, which would risk another breakout. But more surprised that the hivebrooder in front of him didn't jump his bones, or rip off his clothing to attend to his fully-excited malehood.
"And your pheromones do not help matters, I must admit." The Hivebrooder looked down at him, arms crossed in front of her. Even with her arms crossed, she made no effort to hide her breasts. In fact, her breasts rested on her arms, on full display like raspberry gelatin being served for a meal. "And I am aware that the pheromones I am secreting, may be influencing you as well. It is not intentional."
"Y-you are?"
She shrugged. "You are a male. I am a hivebrooder. I endeavor to fight my body's natural responses, but they still happen."
"Y-yeah... S-sorry, then."

"With all of that explained, though, there's still one thing that doesn't make sense to me." Casey was able to sit at the edge of one of the pools of water, where the hivebrooder was taking yet another sip. Casey had been fighting the temptation to drink from the water, unsure if it was really fit for kangaroo consumption. But he didn't doubt that this hivebrooder's immune system was better equipped to take it.
"Name your concern."
"Why me? Me, specifically?"
The hivebrooder lifted her head and looked at the roo. "Among my travels... I had to learn from a distance. As I could not fulfill my evolutionary mandate as a hivebrooder, I busied myself with studying your society. Your culture. It is... certainly much different than anything an Evisceroid is used to."
Casey thought about the workaholic drones and the militantly obedient slashlings. "Yeah, I bet."
"Among the concepts I have been exposed to, and have developed an interest in, are the rituals of... I believe they are called 'courting'? And 'romance'?"
Silence was the only response. The Evisceroid turned to her houseguest to confirm whether she had said the terms right. But Casey sat there with a confused look on his face. "Uhh... you mean dating? And love stuff?"
"I have heard these terms used interchangeably, yes."
Casey was only further confused. "Why... Why those? And why me?"
"From the little I have been able to observe... Your kind has a life cycle not unlike a hivebrooder's. You begin as young larvae, then undergo staged metamorphoses until you reach maturity. What you call 'adulthood'."
The roo fought hard to keep from chuckling. "Well, we don't call kids 'larvae', but..."
"From what I have been able to see, however, there are two levels of adulthood. Physical maturity, and societal acceptance. What you would call... becoming a man."
Casey had no idea what to say, no idea what this alien hottie was getting at.
"From what I understand, the concept of 'romance' has to be learned by involvement. I propose to you... an agreement."
"Agreement?"
"You keep my existence here a secret. You do not jeopardize my safety, or attempt to breed with me. You also teach me and help me to understand the concept of 'romance'."
Casey shrugged, unsure how he was going to fulfill that last one. "Okay..?"
"In return, assisting me will assist you, in that you will be learning of 'romance' for yourself as well. I will also assist you in ascending to societal acceptance... I will help you 'become a man', as you say."
Casey blinked several times, as if clearing his eyes would help him to understand fully what he had just heard. "Wait, so... if I teach you romance... you'll help m... You'll be my girlfriend?"
The Evisceroid blinked back twice. Her expression was stoic, unperturbed. "Is that the term used when speaking of mates? Or is that used for life partners, only?"
"I... guess both? Could be used for both."
Her brow furrowed. "It would not be wise for us to copulate. Just one intercourse would turn my ovipositor into yet another hive factory, right here. It would not be safe for anyone here."
"I... yeah, okay. But no, 'boyfriend and girlfriend' doesn't have to be just for those who... intercourse."
"I... Hmm." She paused, thinking about something. She looked him over again. Casey had his hands covering his crotch, hiding his half-chub ineffectively, but she could smell his scent. And knew he was fighting it as much as she was fighting her urges.
"I... guess we have a deal, then? I'll protect you, and teach you about 'romance', I guess."
Casey held his hand out towards her. The hivebrooder stared at it.
"... I recognize this as... some sort of greeting? Or parting? Or... No, this is for a business transaction, is it not?"
"Uhh... Yeah, the last one. When we make a contract, we... seal it with a -- Okay, either we sign, like, a written contract, or we shake hands, to bind it."
The Evisceroid paused briefly, before extending a hand towards Casey. But not towards his hand. Her hand stopped a few inches from his chest. And then she proceeded to produce tremors in it, vibrating it. Literally, shaking her hand.
"Uh... Here." Casey slipped his hand into hers, then pulled the hand to a comfortable distance between the two. Then he gripped her hand, and lifted it up and down, giving her a formal handshake.
"Ahh. Yes. There. We have an accord."
"Y-yeah, I guess so."
After a few moments of awkward silence, the girl wouldn't make a move to detach from the handshake, so Casey did first.
"So... I'm Casey. Casey Kangaroo's my full name, but you can call me Casey."
"My hivebrooder name is... a danger to me. I have taken up a new name. My name is Theria."
Casey nodded. "Gotcha! Nice to meet ya... Theria."
"As am I pleased with meeting you... Casey."

That night, after yet another chiding from his mother, this time joined by his father simply for skipping a meal, Casey found himself taking a deep-clean shower, rubbing a bunch of fur-wash into his body. With the briefest of pauses, and one peek to make sure the bathroom door was locked, Casey squatted down in front of the shower-head and started stroking himself, jerking himself vigorously.
In his mind, Theria's boobs bounced and filled his field of vision, dripping with sweat. And from the nipples, yellow syrup started leaking and dripping down. Casey imagined he was dwarfed by the hivebrooder, and those drops of royal jelly started dripping down onto him, splashing onto his face and mouth and shoulders. He lifted himself up to meet her bosom, licking her teat, imagining their taste as honey, but creamier. His malehood throbbed as he squeezed it and choked it.
Then he imagined standing behind her, his hands gripping her ovipositor, sticking his dick within her. He imagined she pushed him back towards the wall of her cave, tendrils erupting from the resin-coated walls and holding his forearms and ankles. Casey could imagine, and feel, the sensation of a suction seal around his member, a squelching sound erupting from every thrust.
His imagination led him to seeing that ovipositor inflating like a balloon before him, getting stuffed to the brim with his baby batter. It didn't matter to him that suddenly a flood of eggs shot out and settled around him, surrounding him in a waist-high sea of eggs. And then the sounds of bombs. Then the conflicting feeling of flames as cold as ice. And unearthly screeching.
"Casey? CASEY??"
Casey blinked, finding himself in the shower again. The water had turned cold, and there was a loud rap on the door. His mother was calling his name.
"Casey?! Did you take all the hot water this time?"
"Uh... Uh, sorry, Mom!" He quickly shut off the shower, getting out and grabbing a towel to wrap around his lower half, not noticing before opening the door that he had--
"Did you use your shower time to pleasure yourself?"
Casey paused, then looked down. His boner was putting no effort into hiding itself, even under his towel. Casey could suddenly feel blood rushing into his face, but not fast enough to make his erection go down.
"... At the very least, you didn't masturbate into the drain, right? That stuff will clog up the pipes."
"Uh... I..." Casey looked back at the shower, then at his hand. He doesn't remember if he ejaculated. He remembers the feeling of an orgasm, a nice and intense one, but the other memories, the scary ones, rang in his head for far longer.
"Clean up your mess, honey. Then off to bed. You spent all the hot water..."

Casey sat in bed, this time nervous about what he had seen in his orgasmic moment. Maybe it was just his overactive imagination. After all, the bombs were influenced by the knocks on the door, the coldness was from the cold shower water...
Then he touched his hand. The hand that he had offered to Theria. He rubbed his hands together slowly. He remembered her texture. Warm, but tough. Like her hands were calloused from so much digging.
He smiled to himself. He had to protect her. They had a contract. A secret contract. He chuckled to himself as this thought started carrying him off to a dream's embrace.
And then his eyes shot open as he realized...
He couldn't tell Robbie that he had an alien girlfriend. Oh no.