The death of an astronomer was always a grand, somber event.

It never mattered if the practitioner in question merely oversaw a small country parish or if they were a king's own astronomer; they were all mourned with every bit of pomp and circumstance that could be afforded, and they were always immortalized in The Astronomer's Handbook, which released new published editions each and every time one of them died. The updated versions would include the practitioner's life works, as well as a single piece of wisdom based on the life they had led. This compendium of knowledge was affectionately called "The Astronomers' Last Words" and was widely considered good advice, even if one was not an astronomer themselves.

To date, the "Last Words" included six hundred and eighty seven pieces of advice, one for every single astronomer that had lived and died in the past four hundred years. It was known that astronomers had existed for many centuries before that, but obviously their advice was rubbish and outdated, and no one wanted to read it anyway.

That being said, many of the "Words" were taught to every child before they even learned how to speak, so that it wasn't uncommon for a proud parent to hear their son or daughter shout 'Never sell your shoes for a promise of five pigs!' suddenly and clearly, only to resume the sort of gibberish one normally expects from a child a moment later. Over time, about ten to twenty of these sayings became so universally applauded for their sense that they were renamed "The Astronomers' Lectures" and they went a little something like this:

1. When encountering a strange creature or person upon the road, do not eat anything they offer you. Unless you wish to die, in which case, that's fine.

2. If found alone on a moonlit night, lighting a fire will only draw wolves to your door. There isn't any reason to light a fire when you have perfectly good moonlight anyway.

3. Vampires, Selkies, and Sirens are all tricksters and deserve to have their knees poked. Preferably by angry gnomes. Or seagulls. Seagulls work too.

4. No one likes a negative ninny. Not even Banshees.

5. Do not, for the love of the gods, fall in love with your own reflection because that never ends well.

6. Hearing voices is not a good sign. Seeing things is also not a good sign. Unless the voices and things actually do exist, in which case, carry on.

7. Planets are pointless. They're too round and flat to be of any real use so it's best to pretend they're not there.

8. If you are given a cursed object, throw it up into the air and chuck it at the nearest passerby. Let them deal with it.

And so on and so forth.

These snippets of good advice were all broken by a single astronomer in the year 1432 of the Emerald Star, though no one knows what exactly happened to her because she seems to have died in at least forty different ways, according to the legends.

More recently, there was another astronomer who unknowingly broke at least three of the "Lectures" and subsequently had to go on a very tiring journey that ended in his punching a man in the face.

This is that astronomer's story.

When an astronomer dies and his life's works are shipped off to the nearest printing press for immediate revision, there is one more tradition of great importance.

After spending several days ensuring that every single ritual is carried out properly, the astronomer's apprentice must set the body on fire themselves. It is said that in the moment the flames engulf a master, his student will have a moment of prophetic clarity that will inspire their research for the rest of their lives. They then take their teacher's place as the local astronomer and everyone goes back to mind their own damned business, much to the relief of the grieving and heavily sleep-deprived apprentice-turned-master.

In a small corner of some kingdom or another, there was a small parish whose name eludes everyone because no one really cares enough to look through "The Astronomer's Handbook" to find out. It was a quiet town in the countryside, near the sea, and the astronomer who oversaw the region was named Celestino. He was a nice enough sort, the kind of man who goes into his profession because he thinks it suits his name, and his apprentice was a boy with black hair and brown eyes named Yuuri.

His hair and eye color weren't particularly important, but these details keep finding their way into the stories for some reason.

Now, normally, apprentices were acquired in a variety of ways. Students who were interested from the beginning would pester their would-be master until they gave in; parents would send away a particularly annoying child so it would be someone else's problem; or the master would pick their apprentice themselves.

Yuuri did not fit into any of these categories.

One day Celestino opened the door to his tower and Yuuri was lying on his doorstep, a small boy of about five years old wrapped in an animal skin that smelled like it hadn't been washed in much too long. His first thought was to shoo him away, but he took pity on the child and decided to take him in as his student.

Celestino greatly regretted that until the day he died.

This was because Yuuri, while an exceptionally bright academic, was, to put it bluntly, odd. To begin with, he excelled at all the sciences and at alchemic concoctions, but he could not for the life of him work out even the simplest fetching spell or mix together a magic potion. This was a great flaw in an astronomer.

Secondly, about two years after he was taken under the astronomer's wing, he began a bizarre habit of speaking to himself. Often.

At first Celestino thought he was merely muttering under his breath, the way every academic does when confronted with a particularly perplexing puzzle, but over time he came to realize that Yuuri was speaking with someone, and someone who very clearly did not exist.

As the 'Astronomer's Lectures' so clearly stated, "Hearing voices is not a good sign."

Celestino decided to give the boy the benefit of a doubt, wondering if perhaps he was lonely and needed a companion. One day he set out into the forest and came back in the evening with a small, golden kitten in hand.

"What's that?" Yuuri asked curiously when he saw the small creature mewling in Celestino's arms.

"A cat spirit," his master explained, taking the kitten by the scruff of the neck and placing him on the experimentation table. The cat looked around, obviously bewildered at its surroundings.

"What makes it different from a regular cat?"

"Well, to begin with, it's not a cat," Celestino said, drawing a circle around the kitten with chalk. "It's actually the spirit of a child that died at the same time as a cat, and their souls mixed together to be reborn as this little thing."

"Then it's a baby?" Yuuri asked, watching his master add in the symbols to the outside of the circle.

"In a sense. It will grow, but it not at the pace of a normal living thing. After a few months it will decide what age suits it best and stay there until the end of its life. For now, however, it's just as stupid and helpless as a human child, and unfortunately not nearly as clever as a true kitten."

Yuuri nodded.

"And the circle?"

"A bonding ritual," the astronomer explained. "He's to be your familiar."

"Mine?" the boy asked, taken aback.

"You look like you need one," Celestino said flatly. He didn't bother to elaborate.

He finished tracing a series of complicated figures near the kitten's paws and stood back to admire his handiwork.

"There, that should do it," he said, satisfied. "Place your hands on the circle, Yuuri."

The boy did as he asked, feeling slightly foolish.

Celestino muttered an incantation and the circle began to glow, first a faint blue color, and then a pleasant sort of red, not unlike a beautiful mound of strawberry ice on a hot day.

"For the spell to work, you have to name it," he said suddenly. "It has to be based on your own name, or the bond won't take."

Yuuri blinked rapidly, trying to think of something, anything that would fit the little cat on the table.

He could have gone with 'Yuu', but that was confusing when spoken aloud. 'Ri' had a nice ring to it, though it didn't seem to suit the spirit. 'Uu' was plainly stupid.

So in the end he threw caution to the winds and just said whatever came to mind.

"Yurio."

The kitten suddenly sat alert, staring up at Yuuri with wide green eyes. It blinked once and meowed.

"It took," Celestino said, pleased. "When he's older he'll will be able to hold a human form and talk, so don't be startled if he suddenly starts commenting on things."

"Okay," Yuuri said, holding a hand out to the kitten.

It sniffed at his hand and licked his thumb, only to scratch furiously at him second later.

"Ow! What was that for?!" he cried, pulling his hand away. The kitten gave him a very pointed look that Yuuri clearly understood as 'Why did you think Yurio was a good name for a cat?!'

"I take it back," Celestino said, amused as he watched the exchange with a learned eye. "This one is much more intelligent than a human child or a kitten."

He had high hopes that the familiar would soon put an end to the invisible friend nonsense, but Celestino was sadly disappointed. Yuuri continued to speak with thin air, often laughing or arguing in such a way that it was clear he thought he was having a very real conversation. When Yurio was old enough to speak, Celestino beckoned to the cat and whispered to him.

"Can you see whatever it is Yuuri talks to?" he asked, concerned. If the familiar could see it, perhaps Celestino was the one with a problem.

"Not in the least," the cat said drily, licking his paw nonchalantly. "There's nothing there."

Celestino felt a mixture of relief and disappointment at the familiar's words.

"I thought he would get rid of this silly habit if he had a familiar to speak with," he admitted.

Yurio raised a cat eyebrow incredulously. "He talks to me, sure. But he talks to Viktor too."

"Who?!"

"Viktor. That's the name of his delusion."

Celestino sunk into his chair, feeling drained.

"Dear gods, the boy really is mad."

"One hundred percent out of his mind," Yurio said, examining his claws lazily. "Now if you'll excuse me, Master Celestino, I have a mouse to catch for Yuuri's offering today."

Celestino spent the next sixteen years worrying about the future of his parish. By sacred law, an astronomer could not take on more than one apprentice, and an apprentice could not be dismissed while he still lived. Of course, that clause could be used to one's advantage, if one was the sort of heartless bastard to kill their student, but Celestino, unfortunately, was not. He was actually rather fond of Yuuri, and while his skill in magic remained absolutely useless, the boy's research in other disciplines was very clean and elegant.

He would have made a fantastic scribe, if anyone actually had any real use for scribes.

Nevertheless, Celestino went to his deathbed with uncertainty in his heart. An astronomer played many important roles for their parish; they were doctors, scholars, diviners, alchemists, magicians, and fairly good tap dancers, to sum up their impressive resumes. The villagers came to their astronomers for help and guidance, or, failing that, to at least hear what the weather would be like for the next week. Astronomers made for very accurate predictors of the weather.

Yuuri, however, would be unable to fulfill a number of those roles. He wouldn't be able to do magic or fortunetelling, and to top it off, he was mad as a hatter. Even in his twenties, long after he finally stopped speaking to nothing, he insisted on the existence of the supposed person called Viktor, and he would tell fantastical stories about this man, who was supposedly as beautiful as the sea and ethereal as moonlight.

He was clearly a lost cause, but there was nothing Celestino could do about it. One day he tripped over a haphazard pitchfork and broke his neck, and that was the end of Master Celestino. Several days later, a very exhausted Yuuri set fire to the shroud over his master's body and proclaimed, in a very tired voice, that in the flames he could see a a link of black chains that looked like pieces of coral, but the entire village already knew he was insane and paid him no mind.

Thus at the age of 23, Yuuri became the master astronomer and inherited Celestino's title, tower, and his "Last Words," which were as follows and considered to be very good advice indeed:

Don't leave farming equipment lying around.

Not long after this otherwise uneventful succession, the Mad Astronomer accidentally came across a chest hidden in the cellar of the tower. Inside it he found several empty bottles that smelled suspiciously of sherry and an old animal skin that didn't really seem to belong there.

For one thing, it was rather smelly.

For another, it was of a strange consistency, soft but not like fur, and it was a silvery gray color.

When Yuuri pulled it from the chest, he was enveloped by a warm, nostalgic feeling.

Where have I seen this before? he thought, turning it over in his hands. It was about the size of a large cloak, and he had the sudden urge to throw it around his shoulders.

Yurio suddenly jumped on it.

"Where'd you find this?" he asked, pawing at it curiously. Despite being able to hold a human form, he much preferred life as a cat, though he would shift to his eternally 15 year old human glamour if Yuuri ever needed assistance that required opposable thumbs.

"Dunno. It was in Celestino's chest," he replied, still deep in thought. "Do you know what it is?"

"Looks like some kind of skin," Yurio replied dryly. Yuuri sighed.

"Thanks for the help," he said sarcastically. "I couldn't tell that by the smell alone."

"It kind of smells fishy," the cat added, wrinkling his nose.

"I know it's suspicious just by looking at-"

"No, I mean, it smells of fish," Yurio said, rolling his green eyes in exasperation. "It might be a Selkie's skin."

"A Selkie? You mean... like a seal in human form?"

"Sort of, but not really. Selkies are seals. Sometimes they go up to the surface to frolic around, and they take their skins off so that its easier to walk around. They usually hide them after, because if a human takes their skin and keeps it hidden, the Selkie will be forced to follow them home and live with them. It's one of the most ancient and binding engagements in the world. The only thing that can break it is if the Selkie finds its skin and returns to the sea; if it never does, it will die alongside its human partner."

"You know a lot for a cat," Yuuri grinned.

"I know a lot because I'm your familiar and all you do is read all day. I'm surprised you didn't know this already."

"I've never been good at the magic side of astronomy."

"That I know."

Yuuri examined the skin again.

"So if this is a Selkie's skin... does that mean Celestino had a Selkie partner?"

"Don't be an idiot, you grew up in this tower, you would know better than anyone if Celestino had a secret wife or husband," Yurio scoffed.

"Then... whose is it?"

The cat shrugged.

"It's probably an old relic, the sad reminder of some poor Selkie that never managed to free themselves."

Yuuri grew pensive as he stared at the skin in his lap.

"Do Selkie skins have magic properties?" he finally asked.

"Were you not listening?" Yurio growled. "I told you, they're the world's oldest engagement token. It's a spell that binds two people so tightly together that even curses wouldn't be able to tear them from each oth-"

He didn't get to finish his sentence because a moment later Yuuri swore loudly and jumped to his feet, still clutching the skin.

"That bastard!" he shouted, hurrying up the circular staircase that hugged the tower walls. "That utterly dense son of a bitch!"

Yurio had no idea what was going on. The bond with his master allowed him to sense all sorts of things about Yuuri, but sometimes he couldn't keep up with the blatant insanity. This was clearly one of those times.

Whatever, the cat thought, stretching out in front of the fire and flicking his tail. If it's important enough I'll fin-"

"YURIO, GET UP HERE!" Yuuri screeched. The familiar huffed and very deliberately took his time climbing the stairs.

"What is it now?" he asked as he alighted on the kitchen landing, watching Yuuri leaf through a large tome.

"The Handbook!" he yelled excitedly. "It was in the Handbook all along and I never... Gods I've been blind!" he cried.

"We already knew that. There's a reason you use spectacles, Yuuri."

"No, not that! UGH, JUST LISTEN!" He placed his finger on the page and began to read aloud. "'Vampires, Selkies, and Sirens are all tricksters and deserve to have their knees poked. Preferably by angry gnomes. Or seagulls. Seagulls work too.'"

He looked up at Yurio expectantly, as if his great discovery was the most obvious thing in the world, but his familiar was not impressed.

"Congratulations, you found one of the most common 'Lectures' in all the kingdom," he said sarcastically.

Yuuri groaned and ran his fingers through his long black hair in frustration.

"They're tricksters!" he said loudly. "Tricksters!"

"And?"

"And they all deserve to be poked in the knees by seagulls! This explains everything!" he said tapping his foot in excitement. "Don't you see, Yurio?! I'm not mad! I'm not mad!"

"You are not making a very convincing case for yourself," he noted as Yuuri tied his hair back and feverishly flipped to the section of the handbook on Selkies.

"He was a Selkie all along! I have his skin!" he exclaimed, his eyes gleaming as he read.

A moment later his expression soured.

"I'm going to kill him if I ever get my hands on him. How dare he just vanish?! I have his skin! He's mine!"

"I really have no idea what you're talking about, Yuuri," Yurio said cautiously. He was really starting to worry about his master's sanity.

"Viktor! He's my partner!" he exclaimed, slamming his hands on the table. "I don't know why but for some reason I was the only one who could see him... Oh! Of course! The skin! The magic of the skin's contract made it so I could see him!"

"Okaaaaayyy, but Selkies aren't invisible, you know..." Yurio said slowly, wondering if perhaps the astronomer in the next town over might know what to do for a madman.

"Well Viktor is, for some reason, and I'm going to find out why," Yuuri said as he leapt from the chair and began rummaging around one of the bookshelves. "Help me pack, we're leaving as soon as I find a map," he ordered.

"Leaving?! We can't leave! You're the Master Astronomer!"

"Nobody comes to see me anyway, they all think I'm insane," Yuuri said, waving his familiar's concerns away. "Let Phichit handle it, everyone is always raving about his potions as it is."

"Okay but Phichit is the astronomer for a completely different parish, and-"

"Yurio! Quit talking and start packing! I have a fiance who needs finding!"

Notes:

Asterism: A grouping of stars that isn't part of a true constellation.

Ahem, I present to you, my original AU, where Yuuri is an Astronomer, Viktor is a Selkie, and Yurio is a Furry. Yes, there's a point to this story, and I hope it's a fun one! I can write stuff that isn't suffering too! Thanks for reading, and I'd love to hear from you!