It has been several months since the Kamado family's got killed. The only survivors were Nezuko, a thirteen years old girl who started to train to become a Demon Slayer and avenge her family, and her older brother, Tanjiro, who was turned into a demon. They both lived in Nezuko's master's house. His name was Michikatsu Tsugikuni, one of the most powerful and important member of the Demon Slayer Corp. He was the Moon Hashira and he said he had an idea on who was the one who turned Tanjiro into a demon : Yoriichi. The first ever demon to exist. He made himself a whole army all over the country only to find a way to conquer the sun.

That night, Nezuko was training all alone. Mister Tsugikuni was out, killing demons. It happens multiple times per week so it didn't bother the girl that much. Until she heard noises from inside. Usually, her master wouldn't make so much noises when he came back. She so decided to check inside. Nobody was there but she still felt like something was off. That's why she decided to hide inside a closet, just to see if if the impression of an unknown presence within the house was right.

She heard some whispers but not really audible. Then, someone shouted.

"Father ! Why do we have to come inside that Hashira's house ! If he sees us, he'll cut our heads within a second!" What came after, Nezuko couldn't hear it. It's only when the intruders came near her hiding spot that she could hear them clearly.

"Where the hell is she ?!" The same voice as before screamed. It sounded like a ten years old's voice. Then another voice could be heard

"Don't be so irritated, Kiriya, she might get scared..." Suddenly, the two of them stopped moving and talking for like thirty seconds. Nezuko didn't dare to make a sound, not even breathing during those thirty seconds. They felt way longer though. Then, they ran away so fast Nezuko couldn't see them.

She stood there for a long time before she heard someone else open the door. This someone else entered the room and when she recognized her master, she came out of there.

"What were you doing here, Kamado ?", He asked. Nezuko looked up at him. She didn't really want to talk about the intruders, her master might get angry because she didn't fight those two demons -at least, she thought they were- but at the same time, he'd get angrier if he discovered the girl lied to him.

"People entered the house when you weren't here. I wasn't sure if they were demons or humans so I hid there to see what they'd do.

-How much were they ?

-They were two, from what I've heard.

-Were their names mentioned ?

-One of them was named Kiriya, I think. He called the other one "Father".

Mister Tsugikuni didn't answer but looked around. Nezuko guessed he knew something about those demons but she didn't want to ask him useless questions. The girl will surely know soon enough.

Since her master wasn't saying anything she left the room and said goodnight to see if he had any special reaction and it was the case. He simply said it back, nothing about going to sleep so soon ? Or maybe it was that late ? Nezuko didn't know anymore. The sky was deep black and it was almost Spring... Well she didn't have to think about it and directly ran in her room.

Tanjiro was asleep and looked very cute. He had this capacity to change height and spent most of the time looking like a toddler. Maybe it took less energy ? Nezuko wondered. Apparently, he was very calm for a demon, especially one who hasn't eaten human flesh for months. But Mister Tsugikuni still gave him some meat like pork or beef. Nezuko was thinking about all the kind things he did for the siblings, she had no idea of how to pay him back for all this kindness. But now wasn't time to think about this. Nezuko quickly changed and went to bed. Tomorrow would be another harsh but exciting day.

The next day, Tanjiro didn't wake up. Neither did he the following day. Neither did he for the next six months. But Nezuko kept training. Her brother wasn't dead, just asleep. She was sure he'd wake up sooner or later...it...it was just a matter of time... Mister Tsugikuni kept helping her thought. At least, he tried his best. Nezuko couldn't concentrate correctly because of all the worry. She sometimes didn't eat for days, which isn't the best thing when you're practicing swordsmanship. She used all her free time to check on Tanjiro.

One day, the man came to check on Nezuko when she was struggling to stay awake.

"Kamado.

-Hum... Yes, Sir?

-Take a break.

-What ? Why ?I started to train only an hour ago."

Mister Tsugikuni took the girl's shoulder in his hand and sighted "You're not doing alright right now. I know that. Losing someone is pretty hard and we need to get back to work the sooner possible but... Your way of dealing with this is very unhealthy. I might be strict but I care about your well being too."

She looked at him with a sad and tired smile "I'm pretty sure some people struggle more than me and keep on doing so that's what I should do-

-I am your superior, young girl. You do not possess the right to tell me what to do.

-I...

-When was the last time you ate ?

The girl didn't answer and looked down.

"Come inside, I'm going to cook you something good. You're done training for today."

The Hashira let her rest for some weeks, waiting for her physical and mental state to get better. It luckily did get a bit better for the young girl after some time. She started having healthier abits and started training again in the beginning of Summer.

She continued like this for almost a year. A year where Tanjiro didn't wake up but a year where Nezuko learned to be stronger. She would never be as strong as her master, she knew so, but he did say she would soon be able to join the final selection of the Demon Slayer Corp. The only thing she had to do was....a written test... Nezuko felt really disappointed but if she wanted her brother to turn back into a human one day, she had to do so. Explaining all the details of each of the sixteen forms of this breathing technique... How to decapitate a demon quickly... Everything we know about Yoriichi.... It was tiring but what would've done Tanjiro if he was in her place ? He would've done it, she was sure of that !

When she finished this test, she gave the sheet to her master. He looked amused for a second and Nezuko couldn't understand why.

"Did you really think that was it ?" The girl looked surprised for a moment before realizing it was all a joke and felt disappointed. Mister Tsugikuni opened his mouth again

"You see this big rock on the mountain ? If you truly want to become a Slayer, you have to cut it in half with your katana, nothing more."

Nezuko looked at him in disbelief. She remembered this rock pretty well, the first night she spent here, she climbed it with Tanjiro to talk with him while having a break during the training. He was still struggling with his speaking but he was very human in his way of acting. Well he wasn't one at all anymore but he wasn't trying to eat her either, on that day. Not a single day after either. The rock in question indeed was big. No way a rock could break with only a katana. It would at least take month even with the strength of Moon Breathing.

Tanjiro was still asleep but still alive. Nezuko didn't even finish after six months and she would turn fifteen in around a month. It felt weird to know the Kamado's died three years ago, now to her but that's how life was and she had to go on and break this rock, so she came back one more day to the same place. But something was different. Two people Nezuko didn't know were there. She got afraid but saw they were kids and the sun was there, no way they were demons.

One of the kids was wearing a yellow kimono with a red haori, his black hair were tied and he had a weird looking red mask on his head, no way someone could take him seriously. Then, there was an older looking boy. He was also wearing a mask but his was simply grey, nothing more. He was wearing a black and teal haori over a white kimono. His hair were long with turquoise tips. Nezuko looked at them for a moment before the grey mask boy talked.