I was writing a diary in Demon Slayer, and the butterfly ninja honey glass was broken.

Butterfly Shinobu pulled the hair on the side of her face behind her ear and said, "Well, I came to tell you something." "

What?" asked Su Yu for a brief moment because of her small action, and immediately asked after returning to her senses.

"There will be a nine-pillar training camp in the near future, and the master said that some potential newcomers can participate together, do you want to go together?"

After all, he didn't know what shocking things he had done.

"Nine Pillars Training?" Su

Yu's expression was a little strange, shouldn't this matter be after a long time.

This incident should have gathered the protagonists of the original work, Tanjiro, before the "Infinite City Decisive Battle".

How could it start now?

"This... Why did such a large-scale training suddenly begin, did something happen?"

asked Su Yu, who did not know that his diary had leaked, without thinking.

Butterfly couldn't help but smile and said, "Recently, we got the news of the Winding Lord, and we are preparing to go on a crusade against him, and I plan to take you with me." How

did you get the news of him?" Su Yu's stunned face jumped.

But

his diary exists in the system space, and it is usually not placed outside, so it cannot be known.

Looking at Su Yu's expression, Butterfly Shinobu knew that he was thinking about the diary.

Seeing him puzzled, it made the butterfly laugh secretly.

"You don't care about this," Butterfly Shinobu interrupted his thoughts, "You just say whether you go or not, it's a chance to get in touch with a few pillar-level figures."

"Of course go!" Su Yu said immediately, "but I want to bring a few people." You

shouldn't have any friends from the Ghost Slayer, right?" said Butterfly suspiciously.

"You don't care about this, just say if you can bring it." Su Yu said with a learned smile.

"Good boy, learn from me!" Butterfly

pretended to be angry, reached out to his waist, and pinched a handful of the soft flesh around his waist, causing Su Yulong's teeth to grin.

"Wrong, wrong, wrong. Su Yu hurriedly begged for mercy, and the butterfly endured this before giving up.

"Go to your friend, I believe in your vision, and you can definitely not bring idle people - as for the breathing method."

Su Yu waved his hand, "It's not too late to teach me when the training starts, it's not bad in the past few days, maybe I can find a better choice before then."

"Hmph, I don't believe you can find a better option."

The butterfly snorted softly, and immediately took care of herself.

Su Yu looked at the smiling butterfly ninja, a little out of his mind.

Butterfly Shinobu's appearance is definitely a first-class beauty, and the smile she wore in the past always had a feeling of rejection from thousands of miles away.

"By the way, I'm going to develop a mask that can prevent the cold, can you help me come up with an idea, what do you think can be done?" said Shinobu Butterfly.

"Cold mask..." Su Yu was stunned.

He really didn't understand, this is clearly a measure to deal with the cold and ice ability of the winding

two! Did you really not peek into my diary!?

Su Yu said weakly.

You asked. The butterfly couldn't help but smile and look at him.

"Have you been in my room lately and seen any diaries or anything like that?" Su Yu said.

"No, the little yard where you live obviously doesn't have any books, and you haven't bought them, have you?" The

butterfly couldn't help but say this, and her heart blossomed.

It turned out that Su Yu really didn't know that he could see his diary.

"Ahhh... Such.

Su Yu nodded, he actually asked with the answer, because when he got the diary, the system said that only he could see this diary.

But he didn't know that a copy of the diary would appear on someone else's desk.

"Then let's talk about the cold mask—how much do you know about the Winding Mask?" Su

Yu couldn't say that he knew everything about the Winding Mask, so he had to ask Butterfly Shinobu.

"Now I only know that his Blood Demon Technique can make ice and cause damage to us swordsmen who use breathing techniques," Butterfly Shinobu smiled, "I have a few preconceived designs, let's see how it goes." Butterfly

Shinobu took out a book and handed it to Su Yu, opened it and saw the detailed design of the cold mask in it.

Su Yu only glanced at it a few times before shaking his head.

"No, your masks are just conventional cold masks, which protect the face, but lack one of the most critical things - filter elements."

"What's that?" said Butterfly, puzzled.

Su Yu's major in his previous life was safety management, which involved gas masks and the like, and he also happened to understand the relevant knowledge, so he said profoundly.

"I'm not an expert in this area, if you want me to say it, then I will say a little, but I don't know if it's useful, as I said at the beginning, I'm not an expert in this area." The

butterfly was stunned when she heard this, and after digesting it, a thin anger flew on her pretty face, "You fool me." Saying

that, she pinched Su Yu's waist again, looking at the other party's distorted facial features in pain, and only then withdrew her hand.

"Will you or not, bluntly.

"Yes, it hurts, and your hand is too strong." Su Yu touched his aching waist with a bitter face, looked at Butterfly Shinobu's smiling face, and began to say seriously.

"First of all, you need to set a filter layer in the mask and place the anti-icing object, so that every breath, the cold air inhaled will adhere to this layer of anti-icing.

"But without obvious resistance to the body's breathing, this anti-icing substance can be made using activated carbon." This

time it was the butterfly's turn to endure the circle, "Activated carbon... What is it?"

Su Yu, who was about to gush, froze.

"Activated carbon ... Isn't it at this time?" Su

Yu patted his brain and remembered.

Activated carbon in history, was the first British in 1900 to invent metal chloride carbonization plants to make activated carbon.

It was only in 1917 that it was used in gas masks in the First World War.

Now it's 1915, and before those things happen, the people don't know what gas masks and activated carbon are.

Su Yu made a bitter face, it was difficult to do it now.

Make your own activated carbon?

It's not that simple.

『Ding!』『

Unlock mission: If you learn the first breathing method, you will receive any of the "7-day optional rewards". The

voice that suddenly sounded in his mind made Su Yu slightly stunned, and three option boxes appeared in front of his eyes.

"Physical enhancement: Doubles the ability indicators on the basis of the current body.

『『Sword Art Enhancement: Doubles the ability indicators on the basis of the current sword art. "

Zimu face: a special mask for worshiping gods and jumping ghosts, repelling plagues and avoiding epidemics, the sub-face has a certain protective ability, which can block elemental damage;

the mother face adds the role of concealing the aura on the basis of the literal surface, and with the body method, it can achieve the effect of moving without knowing the ghost. (The quality of the first breathing method will determine the number of sub-faces.) ）』