Perseus Jackson's family tree includes one Kamado Tanjiro. It all spirals from there. [Inspired by Darth Erebus' "Hinokami Kagura"]

"You mean...?"

Chiron nods. "That's right Percy, the Greek Gods exist. All of them."

He expects shock, denial, anger, and many other violent emotions from Percy. What Chiron doesn't expect is a soft inhale with closed eyes, and a gentle sigh.

Percy Jackson shakes his head. "Of course they are. Mattaku mou..."

"You don't seem too shocked." Chiron blinks, absentmindedly registering the Japanese words at the end of his sentence.

Percy smiles, though it is more of a grimace. "Let's just say that my family is used to dealing with...supernatural circumstances."

The Centaur's gaze sharpens to a razor's edge.

A Roman legacy? No. Dionysus hasn't shifted forms yet. Is his family blessed by the Shinto then? Doubtful, or Amaterasu-Ōmikami would lay claim otherwise.

Not once does Chiron's stare leave Percy, and the boy glances back unflinchingly.

The xiphos is awkward in Percy's hands.

Luke has coached many a demigods, but it's the first time he's seen someone so clumsy with the blade.

Percy's grip is horribly wrong, like he's trying to hold the one-handed sword with both of his hands instead.

"Stop that." He taps the kid's shoulders gently. "It's a one-hander, you don't need your non-dominant arm."

Percy's eyebrows furrow. "But then how will I guide the strike?"

What?

Seeing his confused look, Percy elaborates. "You know, how do I guide the sword to slash instead of chop? I don't want to shatter the blade."

Luke wants to laugh. "Kid, that's Celestial Bronze, it won't break to anything but the toughest of monsters."

Percy blinks. "Huh, that's weird."

Luke snorts. You're the weird one here, kiddo.

Luke's seen campers get ecstatic at being claimed by their Godly parent many times, and while he definitely hates the Gods with a fiery passion, a part of him can't help but feel happy that these kids were finally getting the recognition they deserved.

So imagine his surprise when after being claimed by Poseidon (and wasn't that a mess because he actually grew to like the kid, clumsiness and all), Percy went from shocked to absolutely livid.

And yeah, this definitely meant he could sway Percy to their side, but at this point his concern for a friend was the much bigger concern. So he'd carefully extricated Percy from the clearing and brought him to the Big House with Chiron, all the while trying his best to calm him down.

It didn't work.

"So you're telling me," His voice cuts across the Big House's table like a sharpened blade. "That my mom was forced into a life of suffering and difficulty because my Father couldn't honour his word?!"

Chiron looks uncomfortable when he speaks. "Percy, the Ancient Laws prevent your father from-"

"So he willingly chose this path knowing that he wouldn't be there to look after us?!"

Chiron has no answer.

"Oh boo hoo, daddy has other jobs so he can't pay attention to wee old Perry Johnson. Gonna cry?"

For fuck's sake Mr. D. Not helping!

Percy sucks in a large breath, and suddenly the hairs on Luke's body shoot up.

Senses kick into hyper focus while adrenaline floods his body, and Luke has to forcibly unclench all the muscles in his body that scream 'DANGER'.

Even Mr. D seems surprised, his eyebrows having shot to his hairline. His cup of diet coke splatters on the ground, all but forgotten.

Then the sensation ends as quick as it comes, and Percy merely squeezes his eyes shut.

"It doesn't matter. Family looks out for family. Always."

Annabeth didn't understand Percy Jackson.

He was a klutz with weapons, one who could barely get up a parry in time and hardly ever tried to lock blades. He favoured evasion over blocking, which was fine, except when he swung his sword it always came in these weird, sweeping arcs.

The fact that she had to go on a quest with him? Extremely concerning.

The fact that he then refused a magically enchanted sword from Chiron? She was mentally preparing her will.

"It's fine Annabeth, I have everything I need right here." He pats a long sword bag slung over him with a cheeky grin.

She squints. "Where did you have the time to get a custom-made weapon?"

He shakes his head "I didn't. It's a personal one from home."

"What?! Mortal weapons don't work you dolt! It has to be Celestial Bronze!"

Rather than reply, Percy merely laughs, before walking towards the Prius.

Grover bleats nervously from next to her. "Are we going to be okay?"

Annabeth could see her obituary already.

Grover never doubted Percy.

Whatever Annabeth accused him of saying? Didn't happen. Absolute falsehood.

Because really, why wouldn't he trust his good friend, who killed all three Kindly Ones by himself?

It all happened so fast.

One moment, the three of them were staring down the old grannies of death. The next, Percy had unslung his bag, ripped out a katana of all things, and exploded into action.

He ducked and weaved under their attacks with barely a sweat, and with a loud cry of something that Grover didn't understand, Percy thrusted his sword point first into all three of them, like some kind of monster shish kebab.

"How the hell did you do that? Isn't that regular steel?!"

"Family secret!"

"Oh don't you play that card-"

Honestly, Grover was just glad he was still alive.

"Welcome back, coal burner." Ares spoke in perfect Japanese.

Oh?

Percy's eyes narrowed.

"My family has long stopped burning coal. We are but frayed and scattered now." He replied.

Ares' shotgun morphed into a massive two-handed greatsword, and he slammed it tip first into the sandy beach.

"That may be true." Ares spoke, this time in English. "But that was how it all started, no? A legendary killing technique hidden as a dance, passed throughout generations. You're lucky kid, normally I'd just smite you and be done with it, but it's been a long time since I've seen a Breath User. I want to savour this."

Annabeth glanced between the two warily. "Percy, what's he talking about?"

Grover bleated nervously.

"My family." Percy said. "I come from a lineage of swordsmen on mom's side. Back in the Taisho Period, Oni were threatening to take over Japan, and so an organisation was created to kill them and defend the land. Kisatsutai. The Demon Slayer Corps."

Percy clipped his katana to his waist, before drawing it out of the saya. The fresh ring of steel echoed throughout the beach.

Now that Annabeth got to have a closer look, she couldn't help but gasp.

The blade was black, the deep colour of charcoal, though hints of sea-green dots lined the edge, glinting like jewels under the sun. The crossguard was oval-shaped, with a light blue core and black border that depicted waves like those seen in Japanese paintings. The hilt was a mixture of green and blue, in that common crossing design normal katanas had.

Annabeth finally understood why Percy had so much trouble with Greek weapons. It wasn't that he didn't know how to fight, but that he was using his skills with the wrong type of weapon. Katanas were not suited to clashes; their thin blade favoured slicing clean through enemies with finesse, rather than brute force. Edge alignment was crucial to ensuring the success of the strike, much more than with a xiphos.

Annabeth thought back to on the bus, where Percy moved so gracefully it looked like second nature. And that sword was definitely not normal. Was that how he could kill monsters?

"Nichirin Steel." Percy supplied, as though reading her mind. "Don't really understand why, but they have supernatural properties. I figured that if they could kill demons then they could do the same with monsters. I mean, they're all equally ugly anyways."

Her lips tugged upwards at the joke.

"Enough talk!" Ares bellowed. "It's time for us to duel! Don't worry, I'm a magnanimous God. If you can defeat me, I'll willingly give up both the Master Bolt and the Helm of Darkness."

"As if you could beat me" went unsaid.

Percy raised his sword in challenge.

Don't worry mom, I'll save you for sure.

Percy reached deep into his memories, drawing on the one that burned bright as the midday sun.

He couldn't have been more than eight, a barely bumbling toddler. Yet when Sally Jackson performed that dance in front of him, it felt like something he could master.

"Our ancestors used to do this from night to dawn in winter." She had said, and little Percy could only look on in awe.

He grounded his stance.

Lifted his sword.

And Percy Jackson breathed.

"Zen Shūchū!"

The sand beneath Percy's feet exploded outwards as he dashed forth.

"Mizu no Kokyu, Ku no Kata!"

Ares swung his greatsword in an overhead strike, but Percy sidestepped it at the last possible moment.

"Suiryū Shibuki - Ran!"

The sandy beach provided little traction, but that's where the ninth form excelled.

The greatsword crashed into the sand and buried itself deep. Ares tried to wrench it out, but Percy was faster.

"Shi no kata: Uchishio!"

The fourth form: a relentless barrage of consecutive slashes. Ares barely had enough time to block.

The God growled and swung upwards, and Percy jumped high to avoid the attack.

"Hachi no kata: Takitsubo!"

A perfect setup for the eighth form.

The Nichirin blade slammed into Ares' sword, and the shockwave sent sand blasting away from them.

But not enough.

Ares parried, the force being enough to send Percy skidding away.

"You won't get me with such weak techniques! Where's the fire, Percy Jackson?!"

You want fire? I'll give you fire.

Truthfully, Percy's body favoured Water Breathing more, and the Hinokami Kagura always took its toll on him when he used it.

But it was clear that nothing short of his best would be needed to defeat Ares.

Breathe, Percy. You can do this.

Breathe!

BREATHE!

"HINOKAMI KAGURA!"

A single step and Percy was airborne, falling upon Ares once more.

The shock was palpable, but Ares was not the God of War for nothing. His sword was already poised to pierce Percy's throat.

He had to be faster.

Percy's blood roared, and he swung his blade with all his might.

"ENBU!"

The resulting shockwave was immense.

Annabeth and Grover forced themselves to the ground, hands covering their heads as gale force winds buffeted them.

Slowly, ever so slowly, the winds died down.

Both demigod and satyr chanced a look at the aftermath.

Percy stood tall, panting and exhausted, with his left hand holding his chest in a vice grip. But he was alive.

Ares lay kneeling, with a massive wound going from the left shoulder to his right hip. Golden ichor dripped onto the sand below.

Percy Jackson was victorious.