For the next year, Itsuki trained sword basics with the girl during the day and wrote stories at night to bring in enough money for the two of them to live better. The girl handled the chores at the martial hall without complaint to accommodate their stay there.
As her cheeks started getting rounder and her eyes brighter, Itsuki found himself staring now and then, thinking she looked more and more like kanao from the anime. He wasn't sure if it was 100% kanao that's why he called her the way he did
One autumn day, exactly a year later, Itsuki's energy bar finally hit 100%. He got his first skill point.
Without hesitation, he used it on Basic Swordsmanship.
The second it leveled up, his head filled with new movements and muscle memory. He instinctively took a deep breath, gripped his sword, and made a perfect cleaving strike—clean and fast like he'd been doing it for years. It felt weird… like cheating. well, it 'was' basically cheating
Not long after, the instructors at Ren Martial Hall noticed how fast he'd improved. The Hall Master called him in and promoted him to an elite disciple. For the first time since coming to this world, Itsuki felt like he had real support from the system.
Then came his next move.
He started researching the coal market in Flower Street. Public heating mostly used old-style coal blocks. That gave him an idea. He bought a few of those coal blocks, added yellow mud, and messed around with mixing ratios, shaping them into round, hollow cylinders. After more than twenty failed tries, he finally made something that burned hot and steady—honeycomb briquettes.
They were easier to light, burned longer, and had obvious advantages. If he could get them out fast, he could take over the winter heating market in Yoshiwara, use the money for daily medical and better meals, eventually rack up more skill points. With that, all he'd need was to unlock Breathing Techniques and keep upgrading. Demons? No big deal. Hopefully
Still, Itsuki didn't let the excitement go to his head. He knew the coal market was cutthroat, and this kind of invention would get copied fast. Worse, if word got out that he was behind it before he had protection, he could really be killed for it. Coal money was serious money.
But he had a plan.
He showed off the briquettes to a few people in the martial hall during a casual group meal. Word got around, and soon, The hall Dojocho Marume Kurando asked to see him.
The guy was in his forties, seemed easygoing but sharp. When Itsuki explained everything and offered the production method with deals and numbers, the Hall Dojocho immediately caught on. He saw the potential for profit and also understood why Itsuki was giving it away.
If the hall took over production, they could use their connections to crush competition and make real money. In return, he gave Itsuki a generous deal: 20% of the monthly profits, and he officially became the Hall Dojocho's personal disciple. That meant access to secret techniques and personal protection.
This was exactly what Itsuki had hoped for.
From that point on, he stopped writing late into the night, and the girl was freed from her chores. They both threw themselves fully into sword training.
Using his monthly earnings, Itsuki had hall servants bring him ingredients and hired cooks to prepare good and healthy meals he didn't really know how to cook good. Thankfully, Yoshiwara had everything if you had enough money.
He ate good cuisine every two days. Even the cheapest ones boosted his skill energy by around 1%. His progress jumped fast.
By the third year, he had used up three skill points and was already back at 90% on the energy bar.
People around the hall had started calling him "Big Eater" behind his back. Not in a mean way—just confused at how someone his size could eat so much.
Itsuki opened his system panel again:
[Host]: Itsuki[World]: Demon Slayer Corps[Age]: 15[Skill Point Progress]: 90%[Abilities]: Basic Swordsmanship (Lv 2), Flame Blade Swordsmanship (Lv 1)
Flame Blade was one of the hall's signature techniques. It took Itsuki two full months just to get the system to show "Uninitiated." Once it did, he spent a skill point on it and got to Level 1. He could handle a small gang of bandits easily now.
Wanting more points, he ate like crazy and trained even harder. Not just swinging a sword—he added strength circuits, bodyweight routines, sprint drills—stuff from his past life.
He ate four times a day just to keep up.
That "Big Eater" name stuck.
But it wasn't just about the food. His body had changed too. While most of the other students looked lean and light, Itsuki had bulked up. He wasn't fat—his muscles were just denser. His body could take more hits, run longer, and explode with more force.
Even without skill boosts, he was strong. Really strong. Enough that some of the instructors started watching him with serious interest.
And honestly? He didn't mind the nickname. The system matched him pretty well.
But it wasn't just him who changed.
"Itsuki, I brought your breakfast."
The girl who approached had grown too. She was around twelve now, holding three bento boxes—two for Itsuki, one for herself. Her expression was still calm, but there was life in her eyes now. When they talked, her voice didn't feel robotic anymore. She smiled sometimes, even teased him a bit.
Her hair was trimmed into a clean fringe with a ponytail, and her face looked healthy and soft. No longer the dirty, hollow-eyed girl from years ago. She was pretty now. The kind of pretty that makes you blink a little longer than usual.
But Itsuki didn't comment on it. He just said, "Put it in the usual spot, Kanao. I'll be done soon, thank you."
"Okay."
She walked over to the stone table and set the food down carefully.
He had given her the name Kanao. He didn't know her real one, and after being around her for three years, he was now 100% sure—this was that Kanao. The one from the Demon Slayer Corps.
And maybe, just maybe, she was starting to look at him the same way he looked at her sometimes—when she wasn't paying attention.