Becoming a Demon

Kate opened her eyes, finding herself in a vast, black void with nothing but herself. "Where am I?" she muttered.

"You're in my world," a mysterious voice echoed around her.

"Who are you?" Kate shouted, frantically searching for the source of the voice.

"You almost killed yourself," the voice continued.

"Are you that being that's haunted me since the beginning?" Kate asked, her tone a mix of frustration and fear.

"Yes, that's me," the voice replied calmly.

"What is it this time?" Kate demanded.

"I'm not lying when I said you almost died," the voice reiterated.

"Should I thank you, then?" Kate retorted sarcastically.

"No, but what you did was very dangerous. Do you know that you died?" the voice revealed.

"What?" Kate asked, confused. "Then..."

"Yes, the one in Shinobu's house is just a useless shell now and won't last long," the voice said.

"What? I haven't completed any missions there, and not completing them means I won't have anything of value this time," Kate said, her voice tinged with panic.

"Can you feel nothing for the problems you've left behind?" the voice asked, exasperated.

"What problem? As far as I know, the Demon Slayers still succeeded in killing Muzan in the end," Kate explained.

"You really are heartless," the voice said, almost sadly.

"Being alive for too long makes you that way," Kate replied coldly. "How about just bringing me back to the Martial World?"

"Maybe I didn't tell you, but not finishing the main quest means that you failed and now will be punished," the voice said.

"What!" Kate exclaimed. "You didn't say anything about that."

"Don't care," the voice responded. "I will send you again another day and I'll change something."

"Hey, why are you like this? It feels like you act like a child," Kate said.

"A child?" the voice echoed.

"Since you can do things like this, I know that you're powerful, but you do things like how a child would," Kate said.

"First of all, you know nothing about me. Now I do things like this because it's the only option. Plus, from a seed like you, how dare you question me?" the voice said.

"Seed?" Kate asked.

"Yes, thanks to me you're here. Your only job right now is to be strong," the voice said.

"I will be strong and I don't need your help," Kate said defiantly.

"I see. If that's the case, then you can be on your own," the voice said. "If you need anything, just call me."

"Just like that?" Kate asked.

"And it disappeared," she thought to herself as the void started to shatter. "Well, I guess that's okay."

Kate opened her eyes and saw a familiar ceiling. "Is this the Butterfly Mansion?" she wondered aloud. "I'm back?"

Trying to move, she realized she was in chains. "Huh? What's going on?" Kate asked, seeing Aoi nearby. "Miss Aoi? What is this about?"

Before Aoi could respond, Shinobu entered the room. "Shinobu-sama, perfect timing. The Saintess has awoken," Aoi said.

"I have bad news for you," Shinobu said, examining Kate. "I don't know how, but you became a demon."

"WHAT?" Kate exclaimed, confused. "How did I become a demon? Did you experiment on me?"

"We didn't," Shinobu replied. "Once we brought you back here after you collapsed, you suddenly started to transform."

"We reported it to Master, but we haven't received a reply yet," Shinobu added.

"How come?" Kate asked, relaxing on her bed. "Is this the punishment for dying?" she thought to herself. Shinobu noticed her contemplative look and continued, "You don't seem like a typical demon. You still have your memories and don't regenerate like a demon."

"I want a mirror," Kate requested. Aoi handed her one, and Kate saw her reflection: cat-like eyes and a set of fangs.

"Is this because of the Sword Spirit?" Kate wondered aloud. "Is the Sword Spirit an evil technique?"

"We really don't know," Shinobu said. "For our safety and yours, we won't yet remove the chains."

"Can you just put the chains on my feet? I want to practice. I might be able to tell what's wrong with me," Kate said.

"We can't do that," Shinobu replied. "But we will make them slightly longer so you can assume your cultivation position."

"Thanks, Miss Shinobu," Kate said.

"What are you thinking?" Shinobu asked after noticing Kate staring at the ceiling.

"I'm thinking about how I became a demon, or if I am a demon at all," Kate replied.

"What do you mean?" Shinobu asked, intrigued.

"Since I had power when I was still human, was I really human at that time?" Kate pondered.

"That's true. Humans possessing powers is unusual," Shinobu said, considering the idea.

"The Demon Slayers regarded me as a Saint, but what if I'm not? I have the power of Divinity but also an evil-like power," Kate said thoughtfully. "What if being a Saint or a demon isn't who I really am?"

"What do you mean? Are you saying that you're different?" Shinobu asked.

"What if the long war between humans and demons gave birth to me?" Kate suggested, looking at Shinobu. "What if I was sent here to end the war or just to be an observer?"

"Huh, what do you mean by 'gave birth to you'?" Shinobu asked, puzzled.

"To be honest, I don't remember my childhood. The earliest memory I have is waking up by the side of a lake, and the next day Master found me," Kate explained.

"I see," Shinobu said, trying to process the information.

"What if I just appeared out of nowhere?" Kate speculated.

"What about your name? How did you know your name?" Shinobu asked.

"I just knew it, like how I knew my powers," Kate said.

"Even my name is different from all of you here," Kate said.

"Indeed," Shinobu acknowledged. "Then what are you planning now?"

"I don't really know. If I'm right, then what will happen to me once we kill all the demons?" Kate wondered.

"But we can't just let them live for your sake," Shinobu pointed out.

"That's true too," Kate replied, settling into her cultivation position. "I'll just stay here for now as you said."

"Then I'll see you tomorrow," Shinobu said as she stood up.

"Thanks again, Miss Shinobu," Kate said, closing her eyes.

After some time, Kate thought to herself, "The quest hasn't changed. What I need to do is rush this random universe transfer." She looked at the quest panel. "First, I have to kill my own demon," she thought, eyeing the chains. "Hmm, maybe I could just..." Kate bent a part of the chain to free herself. "So, it's that easy," she thought as she let herself go.

Kate sneaked out of her room through the window and jumped from the window to the roof, making no sound. "Nice," Kate complimented herself as she jumped from roof to roof, leaving the village. "I have to find a demon as soon as possible, but finding them will be hard," she thought, staring at the village gate. She decided to head to the mountains and saw a random villager heading back towards the village.

Kate decided to stop the man. "The villager knows that it's dangerous at night, so why is he here?" she thought, jumping down from the trees.

"Who!" the man shouted.

Kate landed in front of him but noticed the man had demonic features. "A demon?" she said.

"No! Help me turn back!" the man said, panicking. "I was just turned!"

"Where?" Kate asked.

"From the abandoned shrine at the north of the mountain," the man replied, pointing in that direction. As he looked back, he saw Kate sheathing her katana. "What?" the man said as his vision faded.

"You're too dangerous for the village," Kate said, as she started running towards the north.

As Kate ran, the quest panel popped up, stating, "1 Side Quest Completed: Kill one Demon. Reward: Random Elemental Cube."

"Elemental Cube?" Kate read, puzzled. "Where can I use that?" She thought to herself as she approached the abandoned shrine. She pressed the rewards, and the panel stated, "You got 1 Fire Elemental Cube."

"Fire?" Kate mused. She realized she could use the Enchantability Chips. "Right, I'll put that on my Spirit Sword," Kate decided. She grabbed the Fire Elemental Cube and noticed slots on the sheath of her sword. As she brought the cube closer, it transformed into a small red orb and stuck to her scabbard.

Suddenly, flames erupted around her, causing her to trip and hit the ground. Kate began refining the fire element in her soul. "Argh," she shouted, enduring the intense heat engulfing her body. "I have to refine it fast," Kate thought, pushing through the pain.

After grueling hours, Kate opened her eyes to find herself surrounded by Demon Slayers, with Mitsuri and Shinobu by her side.

"Are you okay?" Shinobu asked.

Kate realized the time. "The demon in the abandoned shrine!" she exclaimed.

"Don't worry, I took care of it when I saw that you couldn't," Mitsuri said.

"What? I see, that's good," Kate replied. "Anyway, why did you suddenly burst into flames?"

"When I killed that demon, I received a new power, the fire element on my Spirit Sword. Because my sword is connected to my spirit, it burned my soul," Kate explained.

"I see," Shinobu said.

"Anyway, how did you know?" Kate asked, looking at Mitsuri.

"I followed you here. I'm responsible for guarding you, after all," Mitsuri said proudly.

"I see," Kate replied. "Looks like I'm not a demon after all," she added as she felt the sunlight hit her skin.

"We don't know that yet," Shinobu said, helping Kate stand up.

"Thanks," Kate said.

"It looks like you'll get stronger in the future. I also have all the other breathing techniques, so we should head back and train," Shinobu said.

"Let's go back!" Mitsuri shouted enthusiastically.

After some time, they arrived at the Butterfly Estate. "Master's reply came, and he said I should let you go because you're not a demon," Shinobu informed Kate.

"Then what am I?" Kate asked.

"You'll have to figure that out yourself," Shinobu replied.

"I see," Kate said thoughtfully.

"Kate, here is the book of all the breathing techniques," Mitsuri said, handing her the book.

"Thanks, Miss Mitsuri," Kate said as she began to flip through the pages, searching for the fire breathing technique. "Since I can use fire now, I better learn the Fire Breathing first," Kate said, igniting a small flame on the tip of her finger.

"That's a good choice," Shinobu said, nodding approvingly.

A month had passed, and Kate had mastered all the breathing techniques except for the Sun and Moon Breathing. As she practiced switching between techniques seamlessly, she felt confident in her abilities. Sitting beside a tree, she reflected on her progress.

"It's good that my natural talent came with me," Kate thought. "My practice is going smoothly. I can already materialize the breathing techniques, and acquiring the elemental cube and infusing it with my Spirit Sword, which is connected to my soul, allowed me to use fire like my divinity element."

Kate considered her quests. "The side quest to kill one demon changed to kill five demons. I guess what I need to work on now is the Hashira main quest."

"I'm ready to be on a mission now," Kate declared.

"You're right," Mitsuri said, overhearing her.

"We will bring you to meet Master again tomorrow," Shinobu said.

"Why?" Kate asked.

"Since you can go on missions now, maybe Master will promote you to a Hashira," Shinobu explained. "You will be the tenth Hashira if that is true."

"Since it's almost night, let's go and rest," Mitsuri suggested.

"Right," Kate agreed.

The three of them headed back to the Butterfly Estate to prepare for the next day's important meeting.

The next day, Kate, Mitsuri, and Shinobu woke up early to prepare for their meeting with the Master. After a long journey, they finally arrived at the Master's house, where they were greeted by the other Hashira.

"You're finally here," said Tomioka Giyu, the Water Hashira.

"It's good that you're early, Giyu," Shinobu said.

Kate was introduced to each of the Hashira one by one. "Kate, you two already met, but that's Tomioka Giyu, the Water Hashira, and that big man there is the Stone Hashira, Himejima Gyomei," Mitsuri said.

"Nice to meet you, Saintess Kate-san," Gyomei greeted.

"So this is how you look, huh?" said Shinazugawa Sanemi, the Wind Hashira.

"And that is Shinazugawa Sanemi, the Wind Hashira," Mitsuri continued. "She's not like you, displaying her scar from a demon," added Tokito Muichiro, the Mist Hashira.

"You look flamboyant as I imagined, Saint-san," Uzui Tengen, the Sound Hashira, remarked.

"Don't mind them, you just need to be useful and don't worry about your appearance," said Iguro Obanai, the Serpent Hashira.

"It's good that we have a new Hashira. Our chances just increased significantly!" exclaimed Rengoku Kyojuro, the Flame Hashira.

"It's nice to meet you all," Kate said, bowing.

At that moment, Master Ubuyashiki Kagaya arrived, and everyone knelt in front of him.

"We're pleased to meet you, Master," they said in unison.