Princess Mi Amore Cadenza. The Princess of Love and co-ruler of The Crystal Empire. Of course, with such a title and the magnitude of her position, she took it to herself to understand the most she possibly could on the aspect of pony society that she embodied. She studied the science of love itself, from the difference in chemicals in one's sweat when viewing somepony they find attractive to the slowing and calming of heartrates when embraced by someone you're sweet on. She studied the way that the ponies of The Crystal Empire looked at somepony they loved and compared it to the way they looked at somepony they didn't. She studied the differences between the glints and glimmers in eyes when looking deep into the soul of one's prospective partners and how that differed from the look a mare or stallion would give to their colt.
She studied love in the magical sense, in the myriad of ways that sorcerers of the past tried to master love and command it to their bidding, and the ways in which they failed and succeeded. Alchemists could mix a potion that forced at the very least a sexual attraction, but even the greatest of potion masters could not say that they could create love. Even if they could mix the exact batch of chemicals, tinctures, and herbs that could induce the exact same physical effects as love, they could not create it nonetheless. The spiritual nature of love was ephemeral to even the greatest of magicians and the most knowledgeable of alchemists, and it was this love that Cadence was luckily or unluckily a master of from the day she was born. Whether it be being an uncanny playground matchmaker to understanding what exactly would make or break a relationship in the modern-day, she was attuned to Love like Twilight was attuned to Magic itself. Although, Cadence could imagine Twilight being the first unicorn to master love itself. That was just how she operated, after all.
This assumption was only further justified when Twilight and Princess Luna revealed their love for one another. Celestia threw a giant party, and both Twilight and Luna seemed so incredibly happy. Cadence chose not to bring it up at the time for fear of being rude, but her magic wouldn't stop bugging her on that day, trying to warn her of something wrong
with Luna and Twilight's love. Not an issue of incompatibility in the partners themselves or a lack of love between them, but some horrid mix of multiple forms of love mixing together, an incohesive mass of platitudes and pleasantries without the true fiery passion of eternal romance. Cadence figured that it had to have been a mixup, a pony from outside having an argument with their spouse. Something like that could never have happened to Twilight or Luna.
So why was it then, that during the witching hour, Twilight and Celestia appeared in Cadence's bedroom with a POP! and a burst of light bright enough to wake both her and Shining Armor? And more importantly, why did Celestia disappear right after, bringing another round of that horrid transportation spell with her? Cadence, and Shining Armor, now in their sleep-deprived states, chose not to dwell on those matters, and instead focus on the pony in front of them.
"Twily? 's that you?" Stated Shining Armor, whose eyes hadn't yet adjusted to the rapid change in brightness.
"Dear, of course it's her. I can't imagine what would bring her to The Crystal Empire on such short notice, though, and with Celestia in tow? Is it another changeling attack? Sombra's return?" Cadence began to worry, Twilight, as much as she loved her, was a bad omen in a sense. Her appearing uninvited was typically a sign of dangerous times to come.
Shining Armor began to don his armor at record speeds, only stopped from calling the guard to mobilize by his sister's magic.
"Brother, Cadence, I want to learn about love. Not the love you show me as members of your family, or the love that you and Cadence give to your subjects or soldiers, but the love between two special someponies. Could you please show it to me?" Twilight pleaded.
"Show it to her?" Shining Armor asked, sweat dripping down his brow. "Sweetie, I know you said in our relationship I'd have to be open in the bedroom, but I don't think I can show what we do to my little sister," he joked, receiving a chuckle before a glare from his significant other. These were serious matters.
"Pardon him, Twilight. Love is a beautiful, magical mixing of the souls of two special someponies when they establish trust and affection for each other beyond what they'd give to a friend. In a way, it's almost like an addiction. You just can't stop thinking about them, you connect everything in your life with them, and you start to wonder how they might feel about the things that you enjoy, and you believe you can share with them the fact that you do that." Cadence said.
"Yeah Twily, when I'm on guard duty, I just can't stop thinking about Cadence, and the affection I feel for her is different from the pride or sacrifice I give to my soldiers. I want her to love me as much as I love her, and want to make sure she thinks about me as much as I think about her. I value her time as much as my own, and make myself a better person in order to be the kind of stallion that can do that for her." Shining Armor added.
"In a way, love is sacrifice. Sacrificing your time to exactly one pony for as long as you can make the love last. To hold the flaming embers of passion in your heart and keep them even when they're only embers, so that even in the darkest moment, the arguments, the conflicts, it reignites and all is whole again, the two of you, or perhaps more, can keep moving on." Finished Cadence.
"But...how is that different from what I feel with the girls? Whenever I hear a funny joke, I think about how Pinkie Pie might laugh at it. When I see a wonderbolts show, I can imagine Rainbow Dash flying through the exact routine. Clothes? Rarity. Animal? Fluttershy. That doesn't seem to be very different from how you two always think about each other. For my friends, I was willing to sacrifice everything time and time again, even my own life. How is that different from the sacrifice you and Shining Armor give to each other?" Twilight said, clearly unsure of herself. "How can I be certain I'm giving Princess Luna a Love, a part of myself that I'm giving to no one else?"
"Twilight. Who said you had to?" Said Cadence. Twilight paused, the gears turning in her mind. She knew that Love was special. Very special. Powerful enough at least as a magical source to be desired by hordes of sorcerers both good and evil. So how could it possibly be that she could share the same exact love with Luna as she did with the girls? For a moment, it seemed as though something dawned on her before POP! She disappeared, leaving Cadance and Shining Armor with the worst headache and sleep of their lives.