The morning sun shined brightly over the forest area where many members of the demon slayer corps could be seen running. Each one was sweating profusely already despite the amicable air temperature. They all struggled to build up their stamina as their instructor whipped them into shape. Tengen Uzui was constantly nipping at their heels with his wooden swords and "encouraging" the various weaker members of the corps to give this training their all. What they thought was hell now would only get so much worse if they didn't complete this phase of training; however, not everyone was having a difficult time.

Inosuke Hashibira was running circles around his fellow corps members, much to Tengen's delight. The sound hashira had high hopes for his good friends that helped him defeat an upper moon. He was even more pleased that Inosuke had made the challenge more difficult for himself by carrying Susamaru's box on his back the whole way. Susamaru couldn't begin the training at the same time as everyone else, so she decided to make herself useful and agreed to nap in her box as Inosuke carried her through his portion of the training. Tengen liked this idea… in fact he even forced Zenitsu to add a backpack with extra weight as well, much to the thunder breathing user's chagrin. He didn't make the rest of the corps do the same as he knew his buddies needed more of a challenge or else they wouldn't get much out of his training.

Inosuke and the rest of the corps members continued their running with only short breaks for meals. Once night arrived, things became very different as Tengen pulled everyone into the forest. This was when Susamaru arose from her sleep and exited her box to join the others.

"Gah! A demon!" One member shrieked as he looked for a blade before realizing none of them had any during this portion of the training.

Susamaru sighed as she wondered when the demon slayers would all finally remember that she was on their side. Luckily for her she didn't have to explain herself as Tengen quickly wrangled everyone.

"Stop panicking you sissies! She's a friend of mine and she'll be assisting with your training… honestly how do you expect to fight the upper ranks if you piss your pants at any demon. Very un-flashy," Tengen scolded. He was honestly not sure if this training was really going to help everyone else improve; however, he had faith in Oyakata-sama and would do as he was asked. "Now! For tonight's exercise! You'll begin with a mock battle! Everyone except Inosuke and Zenitsu will be fighting against Susamaru!"

"Huh?" Susamaru asked when everyone looked towards her. Tengen then went up to her and whispered in her ear.

"Try not to beat them up too bad… you'll probably be the strongest demon they've faced so I want them to practice. Later, I'll have training for you," Tengen assured her. Susamaru nodded and disappeared into the forest to play her part. For the next two hours, she ambushed each of the demon slayers and struck them with either a wooden sword or one of her temari. She held back so that each one would only get bruised from the impacts; however, none were able to defend against her assault. Eventually, all of the slayers had fallen and were panting on the ground.

"Wow! You maggots have a longer way to go than I thought! I'll have to double the amount of laps you do tomorrow!" Tengen said as he dismissed everyone. "Thanks for the help Susamaru, now I think it's time we start your training," Tengen said as he readied his own pair of training swords. "I figured having you of all people run laps would be useless… you practically have infinite stamina already so instead each hashira is going to focus on training a particular element of your swordsmanship. Once I'm happy with what you've learned, I'll send you to the next one," Tengen explained.

"Alright! Let's do this!" Susamaru exclaimed as she grabbed her wooden swords.

"Oh but there's one more thing… since you have a long way to go in such a short amount of time… this will be a little tougher," Tengen said. As he finished his sentence, Inosuke and Zenitsu jumped out from the trees and began swinging their training blades at Susamaru. She had barely any time to dodge and soon she was defending against all three of the demon slayers before her. Tengen quickly landed a square hit right on her nose and sent her flying into a tree. "You'll be facing all of us every night until you improve. After all, demons don't fight fair as you know and this flashy offense will help hone your reaction time. Oh and don't use your blood demon art… would kind of defeat the point of sharpening your shitty sword skills," Tengen finished his explanation as he readied to continue their sparring session.

Susamaru spat out some blood and blew some out of her nose as she righted it. She then proceeded to take a ready stance before smirking. "This is fine by me! I'll be kicking all of your asses soon!" She said excitedly. This caused Inosuke to laugh in excitement as well as the four of them launched into a training session that would last until morning.

This type of training regimen continued for about ten nights. Each night, Susamaru would block more attacks and get a handful of hits in against Zenitsu and Inosuke. This intense sparring finally culminated in Susamaru landing one solid blow to Tengen at which point he was satisfied with her progress and allowed her and several other slayers to move on to Muichiro Tokito's training.

Once Susamaru, Inosuke and Zenitsu arrived Muichiro was pleased to meet them. They discussed their friendship with Tanjiro and got along well. The mist hashira then proceeded to spar with each one individually. His goal was to fix any bad habits in their swordplay so he wanted to focus on one person at a time. Susamaru found his instruction the most helpful thus far… and when he struck her his blows were a lot lighter than Inosuke or Tengen's. Still, her swordsmanship was among the worst of the corps and so Zenitsu and Inosuke were both able to move on before her. She had to stay with Muichiro for a full twelve days and since his training took place inside an enclosed space she was able train day and night. Eventually, Muichiro was satisfied with her progress and allowed her to move onto Mitsuri Kanroji's flexibility training.

When Susamaru arrived at Mitsuri's dojo, she observed the love hashira forcibly bending other slayers into positions that were entirely unnatural and many of them would scream in pain while she encouraged them. "Oh man… I bet Zenitsu will enjoy this training… the little perv," Susamaru thought as she approached Mitsuri to begin her training. Mitsuri was happy to assist Susamaru; however, they both quickly realized that the point of Mitsuri's training was lost on the demon as she could already move in ways humans couldn't. Still, Mitsuri offered to teach Susamaru a few tricks she learned when developing her own breathing style from flame breathing. They then sparred briefly; however, she didn't believe she had much to contribute to Susamaru's training regimen so they opted to spend the rest of the day conversing.

"I heard you were one of the ones who helped beat upper moon four. Thanks for looking after Tanjiro," Susamaru said as she observed Mitsuri bring out a large plate of pancakes as a "snack" for herself.

"Oh! That was scary! I thought I was gonna die! But Tanjiro and Nezuko went 'pow' and 'chink' and 'bam' and Genya went 'blam blam!'" Mitsuri regaled; however, Susamaru's just smiled nervously as she didn't really understand what the pink-haired woman meant. This caused Mitsuri to sink in defeat as she said she wanted to crawl into a hole from embarrassment. This made Susamaru chuckle. She was surprised she was getting along so well with the hashira so far but she guessed it was because they were all friends of Tanjiro's and that gave them something in common.

As the two of them continued chatting, Mitsuri suddenly asked Susamaru, "Soooooo… do you like Tanjiro?"

"Huh? Of course I do, he saved my life! He's probably the best friend I've ever had or will ever have," Susamaru declared.

"Right right… but I mean do you like him more than that," Mitsuri said as she elbowed Susamaru's arm.

"Oh! Oh… I… don't think so," Susamaru admitted.

"Really? You hang out with him all the time! I would have sworn!" Mitsuri said in shock.

"Well… I care about him deeply, that much is true but… I can't see myself… with anyone," Susamaru explained. "Especially Tanjiro… he's in another world from me. He is practically the Buddha with how kind he is… I'm a monster."

"Don't think like that! He doesn't see you that way at all! He spoke about you a ton in the swordsmith village!"

"He did?!" Susamaru exclaimed in shock.

"Yeah! That's why I thought maybe you two liked each other," Mitsuri admitted sheepishly.

"Well I'm kind of surprised but… no… maybe if things had been different… maybe if I weren't a demon but that's not how life is," Susamaru said.

"But… isn't Tanjiro trying to find a cure for Nezuko? If he does then that means you could become human again!"

"I know but… I'll be honest, I always kind of thought his dream of curing Nezuko was hopeless. I want to support it but… I don't know if I believe it's possible."

"I suppose it is hard to believe… no one has ever been cured before… but still, if anyone can find a way I bet it will be Tanjiro! He seems to always make the impossible possible!" Mitsuri encouraged.

"Heh, I guess that's true… I've seen it firsthand several times. Even so… I don't think it would work out… besides," Susamaru looked around before leaning towards Mitsuri and whispering, "he and Kanao have crushes on each other and it's adorable!"

"REALLY?!" Mitsuri beamed at the idea of Shinobu's tsukugo and Tanjiro being an item. They were both so cute to her that it made her clap her hands in glee.

Susamaru simply nodded. She was relieved the conversation had shifted away from her; however, she wanted a bit of payback for making her feel embarrassed so she decided to ask Mitsuri who she was interested in.

"Oh um… well I…" Mitsuri stuttered.

"Hey you asked me, it's only fair that you answer too!" Susamaru prodded.

"Oh alright… I really really really like Obanai!" Mitsuri admitted.

"Wait… who is he? I don't think I've met him yet," Susamaru asked.

"Oh! He's the serpent hashira! You'll actually meet him next! His training involves increasing your accuracy with a blade!"

"Really? Nice! I could use that!" Susamaru said excitedly.

"Yeah! You should head over tomorrow! I don't think I have much more to teach you anyway," Mitsuri encouraged.

"Sure! Sounds like this will be more what I need," Susamaru replied. Mitsuri and Susamaru continued to discuss the former's love interest for a while. Susamaru was surprised the snake guy she saw at the hashira meeting she attend was someone as caring as Mitsuri described and she looked forward to her next training.

It was not long before the next night arrived and Susamaru waved goodbye to her new friend before moving on towards Obanai Iguro's dojo. She expected to make quick friends with him as well based on all the praise Mitsuri gave him; however, when she arrived she realized that was unlikely to happen. His gaze was full of venom and inside his dojo, a ton of the weaker demon slayers were tied down to the various pieces of training equipment. Susamaru realized this would be one of the worst training session.

"Um… do I dare ask why everyone is tied up," Susamaru hesitantly began a conversation.

"They are being punished for their weakness, sloppiness and for just pissing me off!" Obanai yelled at her.

"Okay… this is going to suck isn't it?" Susamaru just blatantly asked.

"If it doesn't, I'm not doing my job correctly," Obanai replied. He then went on to the specific expectations he had. "By the way don't expect any special treatment. Kanroji said nice things about you; however, you're a demon and that is a sin I will never accept," Obanai stated honestly.

"Good, if I got special treatment I wouldn't learn!" Susamaru replied before readying herself.

"Hmm…" Obanai admitted to himself that she had the right attitude at least. He then began the grueling sparring matches where Susamaru was expected to hit him by targeting the gaps between the other corps members that were tied up. Each weaker slayer begged Susamaru not to hit them which made it harder for her to concentrate. Meanwhile, Obanai easily slithered through the gaps like his breathing's namesake. The training was rough and Susamaru felt guilty every time she accidentally clocked a random slayer with her training sword. Obanai was harshly critical of her every mistake; however, she at least was able to learn the mistakes she was making and over time she did make progress.

After five days of this grueling training, Susamaru was relaxing during one of her breaks when she noticed Obanai yelling at someone and decided to investigate. Outside of the first day, he usually didn't yell as he was actually quite a reserved individual; this meant that someone new had shown up and was getting chewed out and Susamaru wanted to see who it was. She was happy to see it was Zenitsu and Inosuke who had finished their flexibility training! She wanted to say hello to them; however, Obanai and Zenitsu had gotten into a shouting match with each other.

"From now on you stay away from Kanroji you filthy pervert!" Obanai screamed.

"Why so you can have her all to yourself?! I don't think so! If YOU go near her I'll have to duel you to the death!" Zenitsu screamed even louder.

"Why are boys sometimes so stupid," Susamaru thought as she continued observing their little spat; however, she realized it was escalating too quickly as veins began popping out of Obanai's face and he quickly went to strike. Zenitsu with his wooden sword. Susamaru instinctively closed the gap between them and Obanai struck her across the face instead of Zenitsu.

"Susa! Are you okay?!" Zenitsu yelled as he picked Susamaru up off the ground.

"Yeah I'm fine but what is wrong with both of you!" Susamaru said as she wiped blood from her cheek.

"He started it!" Zenitsu said as Obanai grew increasingly frustrated.

"I don't really care, you're both idiots!" Susamaru said as she looked at both of them. "Besides, I thought you had a big crush on Nezuko! Was that just for show?!"

"W-well I… No it's not! I just… never mind," Zenitsu said dejected. Susamaru realized she struck some kind of nerve and relented. She then turned to Obanai instead.

"And you! You're a hashira! You're really going to fly off the handle if someone goes near the girl you like? What are you 16?" Susamaru reprimanded.

Another vein popped up on Obanai's forehead. "If you are going to question me then our training ends here and you can leave!"

"What? All because you're insecure about the girl you like even though she already likes you back?!" Susamaru yelled before placing a hand over her mouth. She realized that Mitsuri hadn't told Obanai that herself yet and that she had just screwed that secret up.

"S-she does?" Obanai asked much more quietly.

"Um… yeah she… kinda told me while I was training with her…" Susamaru figured she already spilled the beans so she may as well explain herself. "She even said all these kind things about you that you did NOT live up to man," Susamaru continued.

"I… everyone is dismissed for the day…" Obanai said as he quickly left the dojo.

"Uh oh! He's still supposed to train me, shit!" Susamaru thought as she ran off to go find and apologize to him for insulting him to his face. Eventually she found him outside starring at the moon later that night. "Um, hey Obanai… I'm sorry for saying you didn't live up to what she said… she really thinks the world of you and with this whole training regimen and how you treated Zenitsu I just had a hard time seeing what she meant," Susamaru apologized.

"No… you don't need to apologize. I'm sure I haven't lived up to her expectations… that's one of the main reasons I've never told her I love her myself," Obanai admitted as Susamaru sat down next to him.

"Oh… I can relate to that sentiment," Susamaru said in solidarity. "Still I have been wondering something, the way she describes you… I wouldn't have expected such a terrible experience for all those other weaker slayers… what's going on with that?" Susamaru asked.

"To be frank… I want them to quit," Obanai revealed.

"Huh? Why?" Susamaru asked.

"Because then they would be safe… they wouldn't risk their lives and wouldn't end up killed by demons… we've lost too many as it is. The weakest members always get killed… I don't want to keep seeing it," Obanai explained.

"I see…" Susamaru now was starting to understand the snake man before her.

"Don't tell anyone about this, especially Shinazugawa. I'll never hear the end of it," Obanai stated.

"Sure, I'll do better about keeping my mouth shut this time… so… am I still allowed to continue my training with you?" Susamaru asked hopefully.

"Yes, we will begin again tomorrow. You still need a lot of work… you hit three slayers today," Obanai deadpanned.

"Hey, one of them flinched!" Susamaru said a defense.

"It doesn't matter, there is another point to typing people up and forcing other slayers to hit targets around them," Obanai explained. "When the inevitable battle commences, every member of the corps will be fighting all at once and we will be at such a massive disadvantage that we can't afford for anyone to accidentally slice one of their comrades. It's something I worry about frequently with how many poor swordsman are in the corps these days… yourself included," Obanai jabbed.

"H-hey! I'm working on it!"

"I know… that's why I haven't tied you up yet… there's still hope for you," Obanai said and Susamaru was pleased as this was the closest thing to praise she had received from him until this point. "Now get some rest, we train twice as hard tomorrow since I cut today short."

Obanai kept his word as the next training session was twice as brutal as the previous one. Zenitsu and Inosuke assumed this had meant that Susamaru had made the situation worse and she didn't bother to correct them as this time she decided to not let her mouth run about conversations told to her in confidence. After another seven days, Obanai felt that Susamaru, Inosuke and Zenitsu had progressed far enough to move onto the next training and even offered a little wave to Susamaru as they parted ways.