Soon enough, it's been quite a while since the pillar training started.

"Tanjiro, remember to breath." I said.

"Un!" said Tanjiro.

I wonder if he can pass this, he's lived near the snow areas before.

Through out 10 to -15 degrees, he seems fine.

At -20 degrees, he has trouble breathing.

(Tanjiro POV)

What is this training? It's so cold it's freezing my lungs, Tokan-san, how do you expect us to pass this training?

'Breath Tanjiro.'

Right, the Hinokami dance! If I breath the way my father did, I could last in the cold further.

Heading deeper and deeper into the forest, it felt like my hands could suddenly fall off at any moment. My foot was deep in the snow, the forest was narrow, and there were traps on the way here. I was almost hit by a tree log if I didn't manage to unclamp my foot from the snow.

The smell of snow gets more intense as I walk further, snow, ice, frost, hail, all kinds of scents similar to snow was filling up my snow. I was walking and slowly I realized something, I was getting lost. Because of the freezing weather, my coordination is off.

(Tokan POV)

Miscoordination is inevitable, use your nose, and breathing. Find the exit, breath to increase blood flow to your heart, by doing that you'll fasten your heartbeat so you won't be in much danger.

My test is the hardest out of all of them, that's what I believe. I do wonder how the pillars would do in this, would they pass?

Tanjiro, if you're able to pass this then you'll have the potential to be on par with me in breathing.

This will increase your accuracy in breathing, to be able to heal internal and external injuries to giving yourself a second chance at life. With Iguro's sword training and my breath training, your sword skills will be in sync with your breathing making you more lethal.

Soon enough, Tanjiro was the first one to pass the test but was instantly taken to the butterfly estate because of his internal injuries. Hypothermia, temporary respiratory system failure, and nervous system entering a state of shock.

Though I visited him.

"Good job Tanjiro." I said as he slept.

"Couldn't your training be a little less harsh?" asked Shinobu.

"Iguro and Sanemi's training harsh too." I replied.

"It isn't as harsh as yours, your training nearly put Tanjiro to death."

"Well, I wanted to improve his breathing. He already has high potential but his breathing is not in sync with his sword skills."

"I see, well you should go back. They should have made into your training by now."

"Okay, I'll see you later." I replied.

Inosuke and Zenitsu were the second and third ones to pass. They also had similar internal injuries to Tanjiro.

Demon slayers would repeat the same torture over and over because they would suddenly pass out due to their nervous system and heart entering a state of shock. Because of this, Tokan was forced to lower the difficulty of the test and you would have to pass -35 degrees.

Due to this change, more demon slayers were able to pass. All of their breathing accuracy increased and their potential was raised. Even other Hashiras would participate but with the final test being -50 degrees. As expected, they passed quite quick since they were Hashiras.

I was about to head to back to the estate when my instinct screamed danger,

Muzan was here.

I immediately rushed to the Ubayashiki Mansion and there he was, red eyes, and cat like pupils.

"Oh Tokan, you're here too." said Muzan.

"What're you doing here?" I asked unsheathing my katana standing in front of Kaguya.

"We're just having a talk, don't get in the way." said Muzan giving my a death threatening glare.

"When I get my hands on Nezuko, my dream will come true." said Muzan.

"You're dreams won't come true Muzan." replied Ubayashiki.

"You seem confident in hiding Nezuko, but unlike you. I have a lot of time in my hands." said Muzan.

"I think you're misunderstanding something, I know something about eternity that you don't." said Ubayashiki-sama.

"It is nothing but human thoughts, thoughts last for eternity. The demon slayers have died out for thousand years but they haven't disappeared at all. Let me prove to you that human thoughts are indestructible, the thought of never forgiving those who take innocent lives away senselessly are eternal."

"You have never been forgiven, not in the last thousand years. And you Muzan have stepped on the tiger's tail countless times, incurring the wrath of the dragon. In essence you have awoken creatures that has been slumbering for a long time, they will hunt you down, and will never let you get away."

"Are you done talking?" asked Muzan as he tries to attack Ubayashiki-sama.

"Emergency Summon! Emergency Summon! Attack at the Ubayashiki Estate! Attack at the Ubayashiki Estate!" said the Kasugai.

'Oyakata-sama' thought all the pillars.

Suddenly, my instincts screamed danger.