Take this, derpybuckingsucks23.

“Luna... Luna... Lulu!”

Her sister’s shout brought the entranced alicorn out of her daydream. Shaking her head to dispel the last cobwebs from her mind, she turned to Celestia. “Yes Tia?”

“You were daydreaming again.”

Luna crossed her her hooves indignantly and put on her best pouty-face. “We were not!” This answer only made her sister’s stare intensify. “Okay, maybe a little.”

The Goddess of the Day rolled her eyes. She knew that her sister had a tendency to nod off during long sessions in Royal Court, but it was beginning to get tiresome having to wake her up every ten minutes. “Lulu, you can’t just ignore your royal duties, you know.

“Look around you.” She swept an alabaster hoof over the room they were in. Ponies of all races milled about hurriedly, buzzing around the throne room like bees in a hive. In the center of the golden-painted hall stood a rather long line of royal ambassadors, couriers, nobles and common folk, all waiting patiently for an audience with their dear leaders. “All these ponies depend on us to upkeep the kingdom. We can’t do that if we’re off in Lulu-land, now can we?”

Luna’s scowl intensified. “Hmm, yes... whatever.”

Celestia couldn’t help but smile at her sister’s pout. While being the more creative and emotional of the royal sisters, Luna could be a royal pain when she was in one of her moods. “Now Lulu, you know that with all our royal powers and privileges come an increased responsibility. We have an entire kingdom resting on our shoulders!” Playfully, she tousled her sister’s eternally starry mane. “It doesn’t help us or everypony else if those shoulders are slouching.”

“Sister, we’re not a foal. You’ve given us this talk a million times too many for our liking. Besides,” she said, shifting away from her nagging counterpart, “We weren’t daydreaming... we were distracted.”

“Uh huh. Distracted by what?”

“Him.” Celestia sat upright in her throne, her ears perked and her eyes bulging. “Him? You mean-”

“Yes.” Luna gazed dreamily over the sea of ponies in front of them towards a small scribe’s post at the far corner of the room. “Over there, third from the wall.” The Day Goddess turned her eyes to where her sister pointed to see a rather handsome young unicorn scribe. He brushed a long lock of marble-white mane out of his face as he spoke to a snobby looking noble.

“Luna, don’t tell me you want to... court him.”

Now it was Luna’s turn to look shocked. “What? Of course not! We have hardly had a chance to properly introduce ourselves yet.” Her eyes suddenly glazed over as she smirked a bit. “Though, maybe once we’ve gotten to know him better we could try. We haven’t been intimate in a long while-”

“Luna!”

“What? You know what they say about unicorns with big horns.” She shrugged.

Celestia hung her head. She always knew she would have to have the talk with Luna eventually - she just wished it wouln’t happen so darn soon. “Luna, I think we need to talk. In private.” With reluctance she turned to the crowd in front of her.

“Attention, citizens!” Celestia hated using her Royal Canterlot Voice, but it was the only way to be heard above the din of the throne room. “A personal matter has arisen, and we must retire for the day. All appointments will be rescheduled for the same time tomorrow. We apologize for this inconvenience.”

A wave of dissent and disappointment roiled through the crowd for a moment before dimming to a distressed mumble. Luna was just as confused as the rest of the crowd. “Tia, why did you just do that? Do you have any idea how far back this will delay our personal plans?”

“Yes, but there is something you need to know about. Come with me, please.” As the throne room slowly emptied the two princesses rose from their respective thrones and headed for their personal bedchambers.

“Tia, what are you doing? First you mess up the schedule for the next month by ending court early, now you drag us off to our bedchambers for some mysterious reason. We want an explanation!”

The alabaster alicorn didn’t respond, rather continued to lead her bemused sister back to her own personal bedchambers. Once there she sat her down on the bed and gently closed the door. “Thank you for being patient, Lulu.”

“Of course. Now, we would love an explanation if you don’t mind.”

“Yes...” Celestia trailed off. Her normally warm smile darkened to a mere morose frown. “Luna, what do you know know about alicorns?”

“Is this a trick question?”

That got a small smile out of her. “No, it’s not. Just tell me all the basic facts of alicorn life.”

“Well, we have horns and wings, we tend to be royalty, there are only three known alicorns left in existence, we’re immortal-”

“Stop.” Celestia held up a hoof. “Repeat that.”

“...We’re immortal? Tia, where are you going with this?”

“Now Luna,” Celestia’s frown returned. Perching herself next to her sister, she draped a regal wing over her withers. “you know that we’re the only ponies in existence with biological immortality. That means that while we never age, everypony around us eventually passes. It’s unfortunate, but natural.”

“Tia, I’m still confused about what you’re getting at.”

“What I’m trying to say is - oh sweet me this is harder than it seemed - you can’t get romantic with others.” she blurted out.

Luna scrunched up her nose in confusion. “‘Can’t’? Why not?”

“We’re immortal, remember?” The white wing around the Princess of the Night reflexively squeezed the two sisters closer. “If we fall in love with somepony, we’ll eventually have to watch them... pass.” She sighed. “I made the mistake of loving a mortal once. It was sweet, for a while. But then came the agony of watching her wither away in front of me.”

The memories she was dredging up were obviously painful to talk about, as evidenced by the thin, glossy tears that welled in the alicorn’s eyes. “It was very hard, and I don’t want my little sister to feel that same pain that I went through.”

For her part Luna just sat there, her mind working furiously to try and process all this new information. “W-we can’t fall in love with mortals? So, the scribe-”

“I’m so sorry Luna. I wanted to break this to you as gently as possible.” Celestia nuzzled her shocked sister, trying desperately to comfort her.

A small whimper escaped her as she began to hyperventilate. “We need some air.” Pushing her elder sister off she stumbled to the balcony and slammed the door open with a quick burst of magic.

“Lulu!” Great, this can’t get much worse. Celestia dashed after her despairing sister, pushing open the door to the balcony and rushing to her younger sister. “Luna please, don’t be so sad.”

“Not be sad?” The Princess of the Night shot her sister an incredulous look. “How could we not be sad? You just told us we can never love anypony!” She sniffled back a tear, the light of the newly risen moon shining off her glistening eyes.

Her was cut off as Celestia giggled lightly. “Luna, I never said you couldn’t love anypony.” Plopping down next to her sniffling sister she gave her a small, almost sad smile. “So what if you can’t love mortals? They’re all crazy anyway. I will always love you Lulu. And I won’t be going anywhere anytime soon.”

“You know very well that we are talking about romantic love, not just family love,” Luna said as she rolled her eyes.

“Mhmm, who said I wasn’t?” Before Luna could react, her sister leaned in and pressed her lips against hers. The Princess of the Night opened her mouth to scream but found herself muffled as Celestia seized the opportunity and slipped her tongue into her mouth.

The two hung there for some time, suspended by shock and passion, locked together at the lips. Luna’s mind had pretty much exploded into a charred husk incapable of rational thought, leaving Celestia to do the thinking for the both of them. Mhmm... this is nice. I should’ve done this sooner. Lulu’s a nice kisser.

Finally she pulled away, leaving a thin trail of saliva dangling between their lips. “Falling in love with mortals will only lead to heartbreak. I, on the other hand, will never leave you,” she said with a giggle.

Her sister was not faring well. Her eyes contracted at odd sizes. Her hair, normally caught in a non-existent breeze, now hung limp at her shoulders with a few strands bent and curled like broken guitar strings.

Celestia waved a hoof in front of her sister’s thousand-mile stare. “Lunu? Are you alright?”

The burning train wreck of Luna’s mind somehow managed to reply, “You. Kissed me.”

The day goddess stifled another laugh. “Yes, I did. Did you enjoy it?”

“I - uh - you. Just kissed me. Your sister.”

“For a pony so keen on using her Royal Canterlot Voice, you really are tongue-tied right now, aren’t you?” When she received only a small nod in reply, the elder sister sighed before moving alongside her shocked sister, draping a wing over her.

“Lulu, I want you to feel that same glorious thrill that comes with loving another pony romantically. But I don’t want you to feel any of that pain that comes with losing that special somepony. Can you find it in your heart to give me a chance?” She put on her best pleading look, batting her eyelashes and mustering a big set of puppy-dog eyes.

Luna sat there, eyes darting furiously as her mind slowly reclaimed cognitive thinking skills. “You and me... together... isn’t that incest?”

Celestia shrugged. “Well, yes. But it’s not technically illegal, just frowned upon in certain company.”

Luna was torn. She really did love her sister more than anything else in the whole world, but that glaring word incest cut deep into her mind. The thought of it alone put a bad taste in her mouth. What would the citizens think if they came out as an incestual couple (and homosexual to boot)? They might just muster up the nerve to depose them from rule!

“Don’t worry about anypony else,” her sister piped up as if she could read her mind. “We’ll keep this strictly between us.”

Her mind, still half-broken from the kiss, again weighed her options. One side of her mind took the form of her sister, smiling joyously as she accepted her offer. The other took the form of a torch-wielding commoner storming the castle to usurp her from power.

“Well?” The Goddess of the Day was finally showing the slightest hint of impatience.

Finally, the darker alicorn nodded her head slowly. “I... think I would like that.” A furious blush crept onto her face, sticking out like a sore hoof against her rich blue coat. “Just one thing though.”

“Yes?”

“Could we... kiss, again?”

Celesita smiled warmly as she drew her sister closer. “I couldn’t imagine anything better.”