A/N- Before we do this chapter, I'm going to go over your breathing forms, so that when I mention them in the fight, you won't be confused. I'm not too great with writing up these things as this is my first Demon Slayer related fanfic so I may make a few mistakes along the way with describing the forms. If I do, please forgive me, none of these mistakes are intentional. Also this chapter has blood in it so if you're sensitive to that type of stuff then just be forewarned. And now onto the breathing forms.

Y/N is the master of a breathing called Moonlight Breathing. It's quite beautiful when done properly, but it does take a lot of focus and relaxation to maintain and perform perfectly. This breathing technique has six forms, and the final form is quite strong indeed! The forms are as follows:

Form One: Crescent Dive: Basically the same as Tanjiro's Water Wheel one, except that instead of a full circle, Y/N will swing her sword in a crescent formation, and if there is ground blocking her, the sword will go through the ground as if it is water. It is a strong attack, but it has limited range. This is the most basic of the breathing forms.

Form Two: Full Moon Dive: Now this is exactly the same as Tanjiro's Water Wheel one. Y/N will rotate her sword in a full circle, cutting through any enemies in the radius of her strike.

Form Three: Falling Star (this form is reserved for enemies that have surrendered, to let them die peacefully and without much pain.)- Y/N will slash her sword forward, and light will fall in fractals that look like falling stars. If the stars hit the enemy, they cut through skin, muscles, and bones almost instantaneously, so if aimed at a sensitive area of the body, the enemy will die almost immediately with little to no pain, just a weak pinching feeling.

Form Four: Moon's Revenge: The breathing form is started the same way as Falling Star, with a forward slash of the sword, or even a throw of the sword if the enemy is close and your aim is good. Lights shaped like crescent and full moons will fly outwards from the sword and strike the enemy. This attack has a wide range, and the damage the moons do vary by type. Y/N can call a full strike of either crescent or full moons, but full moons deal the most direct damage. Crescent moons deal damage over time with small cuts, and full moons deal a lot of direct damage all at once.

Form Five: Supernova: Y/N will spin her sword in a circle and throw it at her enemy. If it impacts them and stays on them for a minimum of five seconds, the sword will explode and deal a lot of damage to the enemy. This sword form is only used in an emergency, as it totally ruins your sword and will make you have to get a new one (and that's torture for your swordsmith lol)

Form Six: Dark Side of the Moon: This technique will seriously damage the sword wielder, and leave them unconscious for at least a day with lots of annoying cuts at best- at worst, which happens usually, it will kill the wielder. Y/N has never used this form, but she has learned it, and is willing to use it in emergencies. Since she has never used it, and has never seen anyone use it, she cannot describe how it works. She only knows that when the time comes to use it, she will know how. It has to be that way.

And that's all the descriptions! Sorry this is so long, but I hope it helps make sense of what's happening in this chapter. Now, on to the actual story. By the way, I'm absolutely terrible at writing fight scenes, so if this chapter is totally boring or makes no sense, I'm sorry. This is pretty much all a fight scene to the very end lol. (also i just realized that Rengoku, the Flame Pillar, is just not included earlier in the story. just pretend he's dead or something lol, i can't be bothered to edit him back in. he's a good character tho, he's cool. i'm sorry i forgot him)

Everywhere you looked, there was blood and chaos. The hashira had done a good job of executing all of the demons so far, but more and more kept coming. You had been pushed into the back of the advancing group of the hashira, who believed that attacking was the best strategy. As the rearguard, you hadn't experienced much fighting, which wasn't normal for you. You were used to fighting a lot, and never letting up your force. This type of fighting, just guarding the rear just case any enemies happened to come up near you, was annoying for you.

So, in true Y/N fashion, you chose to charge forward, and abandon being the rearguard.

As soon as you went forward, you noticed the difference in the fighting. The more aggressive hashira, like Tengen, Giyuu, Obanai, and Sanemi, were in the front fighting back enemies from trying to attack the weaker ones, like Mitsuri, Muichiro, Gyomei, and Shinobu. The demons up front were more aggressive ones, and you noticed that some of them were even carrying weapons, such as swords and daggers. The weapons were rusty and old, but they still dealt damage, and if they were rusty, they might even deal more damage if the rust got into someone's cuts.

You shoved Tengen and Giyuu aside, and you heard them snapping at you in derision, but you didn't mind. You had to be up front and fight, to show Muichiro, and all the other hashira, that you were strong and that you deserved to be among their ranks.

When you pushed past Obanai and Sanemi, they were more attentive. Obanai called for you to go back to where the others were, so that you didn't get hurt, and Sanemi tired to grab you and throw you back, but you brushed them off as if their concern was worth nothing. Finally, you were in the front, and you were leading! This was your dream!

You took a deep breath and held your sword tighter in your hands. You were shaking in fear, but taking deep breaths helped your fear disappear. Slowly but surely, you regained control of your wits, and you were ready to fight.

"Moonlight Breathing, Form Two, Full Moon Dive!" you shouted, throwing yourself into the midst of a circle of demons and activating the second form of your breathing. Your sword rotated around in a circle, and you moved forward, activating the form twice more to take care of all the demons that were around you. Thanks to the fact that there wasn't much space that the demons could take up, the sword circle dealt a lot of damage, since, as long as you moved forward and activated the form again and again, you would kill at least one demon. This form took a decent amount of strength out of you, but you would be okay.

You heard a male voice crying out in pain, and spun around to see Giyuu clutching a bleeding wound in his side. Obanai had put himself in front of Giyuu, and Sanemi was behind him, acting as shields so that he could bandage his wound and disinfect it, but all the demons smelled the blood and were heading towards it like sharks. Even two hashira couldn't kill a mass of a solid 120-something demons by themselves. They needed help. And you would be the one to deliver it to them.

You lunged forward, slicing four demons' heads off in a row. Then you whirled around on the tips of your toes, slicing two demons' legs off, making them fall to the ground, then cutting their heads off right after you knocked them over. When you turned around again, you noticed that a horde of about thirty demons had broken off from the main group and were running towards you, bloodlust in your eyes.

But you hadn't been hurt... had you?

You felt a flash of pain in your hip, and looked down to see blood pouring out in sheets down your leg. One of the demons happened to have a lance, and they'd somehow stuck it into your hip without you noticing. Adrenaline had been flowing through you earlier, so you probably hadn't felt the pain of the strike. But right now, with most of your adrenaline gone, all you felt was pain. You were going to fall to the ground and be helpless soon, you knew. So you might as well go down with style.

You took five deep breaths- more than you'd ever taken- and cried out, "Moonlight Breathing, Form Six, Dark Side of the Moon!"

Immediately, you collapsed to the floor, dropping your sword. Light was practically exploding forth from it, piercing the demons that were clawing at you as if it was a solid object, as sharp as a knife. As the light began to fade from your own eyes, so did the light of the sword, until a darkness deeper and more ominous than any shadow expanded forth from the hilt of the sword itself.  You felt warm hands touching your hip and thigh, and heard Muichiro calling your name faintly. When you looked up, your eyes met his gray-blue ones, which were shaded over with tears and worry. He was sobbing quite a lot, and you didn't know why.

The darkness that was coming from the sword hilt had expanded to a range roughly twice as much as your Full Moon Dive, and it seemed to be reaching up to the sky, dyeing the white clouds a menacing gray. You watched, as your consciousness left you slowly, borne away on waves of pain, to see what the darkness would do. Would it explode, sending a shockwave of immense force through your enemies and killing them on contact? You didn't know, and you were eager to see.

"Y/N... please don't leave me," Muichiro sobbed, laying his head down on your chest. "I... I'm afraid..."

You reached out to touch his cheek and caress him, not wanting to make him feel lonely.

All of a sudden, the darkness did exactly what you predicted it would do, exploding in a shockwave that picked you up and slammed you into a nearby tree. All the pain and stress piled up, and you lost consciousness shortly after.

The last sight you saw was Muichiro, lying next to you, unconscious.