1563, Sengoku Period

Yoriichi Tsugikuni and his brother Michikatsu had just slayed two demons and were battling a third together. This third demon yelled at the two brothers, "You won't get me! I'll just run away and get my prey elsewhere, so get the fuck out of my way!"

"Oh, really?" Michikatsu gave a small smile as he said to the last demon of the three, "This is where the fun begins, I suppose. Those last two demons weren't much of a challenge. Let's see if you are."

"Time to put an end to the two of you!" The demon then charged forward at the brothers. "Die, bastards!"

"Breath of the Sun, Fourth Form: Burning Bones, Summer Sun!" Yoriichi then used a large circular slash that easily decapitated the demon before he had a chance to strike either him or his brother. As his head flew off and landed on the ground, Yoriichi said, "Nii-san, let's start heading back."

"Agreed," Michikatsu replied. "I'll tell you, these demons are starting to bore me. I want more of a challenge." He thought to himself, "And then maybe I can get a chance to shine in front of him. He always likes to show off."

"Be careful what you wish for," Yoriichi warned him. "You aren't as experienced as me, nii-san."

Michikatsu replied, "It always feels odd being told that when I'm the older brother."

"I get that, but when you're in the Demon Slayer Corps, experience matters over everything else."

"Right, right."

Then, Yoriichi's crow came flying down and stopped in front of the two brothers. "Caaw! Message from the Oyakata-sama! He wants you two to see him as soon as possible tomorrow morning for an important meeting!"

Michikatsu asked, "An important meeting?"

"Indeed," the crow replied. "No other information! No other information! Meet with the Oyakata-sama tomorrow morning! Tomorrow morning!"

…

The next day, the two brothers met with the head of the Demon Slayer Corps at the time, a young man by the name of Ubuyashiki Shiro. As the two bowed in respect, Shiro told them, "Thank you for coming on such short notice, Yoriichi and Michikatsu. Apologies for the suddenness of the message."

"No need to apologize to us," Michikatsu insisted as the two sat down. "You are our leader, after all, Oyakata-sama."

"Very well," Shiro replied. "Now, the reason I've called you both here is because I want to appoint you two to the High Council. I want to diversify the council and include more than just High Priests. The plan is to select around nine of the greatest swordsmen in the corps and put them on the council. They will be second only to me."

"I see," Yoriichi replied.

"With those breathing styles you two have created," Shiro explained. "I feel like we need a more formalized ranking of the best slayers for each breathing style. I'm already hearing talk of people creating offshoots of the five basic ones."

"Offshoots? Already?" Michikatsu was curious. "So they're already modifying an inferior version of the Breath of the Sun, making it more inferior…"

"I wouldn't say inferior," Yoriichi insisted. "The other breathing styles are all really good, nii-san. Don't dismiss them so easily."

"He's right, you know." Shiro then explained, "With this, the nucleus of my idea will be a reality. I've also come up with a name. How does Pillar sound?"

"Pillar?"

"I think it sounds great," Michikatsu replied. "We will be the core Pillars of the entire Demon Slayer Corps and these new ways we can fight demons, so it does fit."

"I have to agree with my brother," Yoriichi agreed. "The name does sound fitting, now that I think about it."

"Glad to hear it," Shiro nodded. "Pillar it is."

…

The next day, as Michikatsu was sharpening his sword, he heard a knock at his door. "Hmm… Who could that be?" He was not expecting any visitors, and as he got up, he made sure to grab his sword just in case it was an attacker. Even during the day, there were plenty of humans who were just as bad as demons, after all. As he opened the door, he was shocked by what he saw on the other side. "Wha… What?!"

"Michikatsu," his wife told him as he held his seven-year-old twin sons in her arms. "It's me, Tenko."

"Te-… Tenko?!" He was amazed to see his wife again after having left her six years prior. "You're back!"

"I miss you," Tenko told her as she put her sons down. "Michikatsu, I know we split up in not so great circumstances, but…"

"You need a place to stay?"

"Yeah," Tenko replied. "Please."

Michikatsu sighed. "Very well. You're welcome to stay."

Tenko was surprised to see him take it so well. "Wait, that's it? No discussion, nothing?"

"I'm okay with it," he insisted. "Come on in."

"Papa," said one of his sons. "Are you my papa?"

Michikatsu felt a small amount of pain at his own son asking him if he really was his father. He knelt down and hugged both of them, telling both, "Yeah, I'm your papa. I still remember you two, Yuichi and Masaru."

Masaru, who had asked the question, replied, "Okay."

Tenko smiled. "I see you held true to your promise."

"Of course," Michikatsu replied. "Even if we fell out of love, these two are still my kids. Of course I'll always love them." He then split from his sons and told Tenko, "Now, let's get your things unpacked, Tokito-san."

…

The next day, as Yoriichi practiced in his garden with another slayer who was around twenty years old and utilized the Breath of Wind, he heard his crow come flying down with another message for the both of them. "Caaw! Tsugikuni Yoriichi-san and Sasaki Toshihiko-san! Mission! Mission!"

Toshihiko asked the crow, "Mission? What for?"

"In the village of Taiwa, approximately six ri to the southwest! Demon! Multiple demons, in fact!"

Yoriichi sighed as he sheathed his sword, "Sasaki-kun, let's get ready." He then asked his crow, "What time do they want us to be there?"

The crow replied back, "Within five hours!"

"We can make that work," Yoriichi replied. "Grab your naginata, Sasaki-kun. You're still inexperienced with a katana like me. Take that, too, though."

"Take both? Got it!"

Yoriichi said to the crow, "Tell Michikatsu-niisan as well if he hasn't been notified."

"He's been notified as well," the crow replied.

Yoriichi then ran in to grab another weapon of his that he had recently purchased. "Time to break this in." He grabbed a Portuguese arquebus that he had received a few weeks prior but had never taken out into combat.

Toshihiko asked him, "Are you really grabbing that foreign hand cannon thing?"

"It's called an arquebus," Yoriichi told him. "And I figured that it's time I finally use it in a fight."

…

Yoriichi, Michikatsu, and Toshihiko arrived at the outskirts of the village of Taiwa at the very start of dusk. Yoriichi instructed them both as they looked around for any signs of demons, "Nii-san, patrol the area to the west. Sasaki-kun, take the area to the north. I'll patrol the village itself."

"Understood," Toshihiko replied as he pulled out his naginata. "Multiple demons won't be an issue with us here."

As he walked away, Michikatsu asked his brother, "Are you sure you want to go alone? What if those multiple demons all pile up on you?"

"I'll be fine," Yoriichi insisted. "I'll have my crow fly out and find you guys if I really need help."

"Are you sure?"

"Yeah," he again insisted. "You don't have to worry about me all the time, nii-san. I can stand on my own."

Michikatsu smiled and told him, "You'll always be my little brother, Yoriichi. I'll always be worried. That's what big brothers do."

Yoriichi chuckled. "Oh, come on."

…

A few minutes later, Toshihiko was snooping around the forest surrounding the village, keeping his eyes wide open for any demons to be seen. He thought to himself as he passed by the trees, "I wish we had more information about what we were getting ourselves into. Multiple can mean two demons, three demons, four demons, five demons, or even a hundred of the fuckers. If it's more than four or five, we'll need more help. I know most demons don't congregate at that scale that much, but you never know." Then, as he heard rustling behind him, he turned around, only to find that a tree had been almost completely cut through in an instant and was now beginning to fall towards him. He yelled as he jumped out of the way, "Shit, the tree!"

As the tree slammed onto the ground, he stood in shock, amazed that someone had managed to fell the tree with seemingly no trace of their presence afterwards. Then, the person who had done it made their presence known when Toshihiko heard another man say out loud, "Hello there, Demon Slayer."

"Wait, what?!" Toshihiko turned around to find a demon whose left arm had turned into a long and giant saw standing before him. "Who the fuck are you?!"

"I'm one of the four demons in the area," the demon explained. "It seems our teamwork has attracted you bastards to the area."

"I'll have to slay you," Toshihiko told him. "So, was it you that fell the tree that almost hit me?"

"Indeed. That tree was supposed to hit you, but I suppose I can't always be that lucky." He then charged towards Toshihiko. "Let's see if I can saw you in half instead!"

"Breath of Wind, First Form: Dust Whirlwind Cutter!" Toshihiko then swung his naginata in a way to produce a horizontal cyclone pattern, slicing off the demon's saw arm and slashing him across the chest. As the demon yelled in pain, Toshihiko told him, "It won't be that easy to kill me!"

"No, it won't. You're right about that!" He then pulled out a kama, a farming sickle he was using as a weapon, and charged again at Toshihiko. "How about this?!"

"Breath of Wind, Third Form: Clean Storm Wind Tree!" Using a whirlwind of slashes all around, Toshihiko deflected the demon's attack before making a swipe at his neck with his naginata. "Here I come!" He managed to successfully score a hit, taking the demon's head clean off at a relative distance than if he had been using a katana like Yoriichi and Michikatsu. As the demon began to disappear and fade away, Toshihiko breathed a sigh of relief and said to himself, "Well, that's one down, and three of them to go. I better tell Tsugikuni-sama and his brother about the other three."