After they got back to the Corps Headquarters, Tanjiro and Muichiro were taken to the Butterfly Estate for their injuries. The whole Kamado family refused to leave their human member's side, so Shinobu was forced to give them a room next door, with Futons for them to sleep in. While they slept though, she secretly took blood sample's from each of them to test. Each day or night, the Demon's would wake at random times to check on Tanjiro, but he stayed asleep.
It was like the human and Demon's situation's had switched. Whereas Tanjiro was the one who'd woken up everyday during his two years of training, while most of his family slept the whole time, now Tanjiro was the one in a Coma, while his family waited anxiously for him to wake. Shinobu assured Kie this was normal after such extensive injuries, but the Demon Mother still looked anxious. Despite their own nature, she knew it wasn't normal for Tanjiro to sleep this long.
When Kie wasn't sleeping or caring for her other children, she spent her time brushing Tanjiro's hair, and singing at his bedside. She worried for her human Son, so much. Shinobu periodically checked over her fellow Hashira, assuring Kie that he was healing well. It was a little hard for her to understand everything that the Human girl was saying, but she did understand that Tanjiro was healing. And that was enough to calm some of her worry. But not for her other children.
Rokuta refused to move from his Oldest Brother's side, clinging to his medical Kimono with his tiny clawed hands. Hanako and Shigeru would peek in through the door several times a day, worried looks on their faces. Takeo would sit on the foot of Tanjiro's bed, staring at him and waiting for him to wake. Muichiro visited, and apologised to Hanako and Kie for trying to attack the young Demon girl. He watched Tanjiro with worry in his newly brightened eyes for half an hour, before he had to leave to rest due to his own injuries. Genya and Teiko also came to visit, Teiko hiding from the sunlight in her bag.
Zenitsu and Inosuke came to see him at different times, and the boar-masked teen had to be chased out by Aoi most times. Inosuke mostly wanted to fight the Demon Kamado's. Kie watched him until he was out of sight, before going back to her sleeping Son. Two months passed like this.
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Tanjiro slowly blinked his eyes open, feeling exhaustion trying to drag him back into unconsciousness. But the weight on his chest caused him to glance down. Rokuta was laying on his chest, fast asleep. Tanjiro smiled gently, and slowly raised a hand to place on his baby Brother's back. "Rokuta" he muttered softly. He glanced over the room to find Takeo curled up and sleeping on the foot of his bed. The door suddenly opened, and the Hashira glanced up to see his Mother walking into the room with Nezuko, Hanako and Shigeru.
"Mom. Guys. Morning" he said weakly. Kie practically teleported to his bedside, with his Sibling's hurrying over as well. "Tanjiro," Kie said, gently caressing his cheek, "are you okay?" she asked with concern in her light purple eyes. Tanjiro felt tears form in his eyes, as his Mother spoke a full, clear sentence for the first time in three years. "I'm tired" he replied. Kie brushed some hair out of his face, "you can sleep more dear, we won't mind" she replied. The young Hashira started to bawl his eyes out, reaching up to his Mother.
The Demon woman didn't hesitate to scoop her eldest child up into her arms, Rokuta still snuggled in Tanjiro's. It took half an hour for him to stop sobbing.
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One week later, Tanjiro was back on his feet, doing light training and spending his time playing with his Sibling's in the bright sunlight. That day, he got a summons from Lady Amane. "Sorry everyone. I have to go to a Hashira meeting" Tanjiro apologised. Then he read a bit more, and blinked in surprise, "oh! Lady Amane wants me to bring all of you with me" he looked up at them and smiled, "okay, let's go everyone!" Tanjiro said with a smile.
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Tanjiro and his family ended up in another Hashira meeting. "Hi you guys!" Mitsuri squealed, waving excitedly to the Demon children. Nezuko went over to the pink and green-haired woman, hugging her. Hanako and Shigeru hugged Tanjiro as they knelt beside him. Tengen grinned, "good to see you again Tanjiro! You took out another Upper Rank! You are one flashy guy!" the former Hashira cried.
"Yes! You are truly a prodigy young Kamado!" Kyojuro added. "It wasen't just me. My family helped a lot. Along with Mitsuri and-" Tanjiro paused. He remembered what Genya had said to him while they were talking, "I haven't been able to tell our big Brother about Teiko yet. I saw him once, and tried to tell him, but- he was so angry about me being a Demon Slayer, I didn't have a chance to tell him about our Sister. And with how he reacted to your family, I'm honestly worried about how he'll react".
'That should be something the Shinazugawa Siblings speak about in private. Even as Genya's friend, I don't have the right to spoil that. Especially since it might result in some bad consequences' "ah, sorry, never mind that last part" Tanjiro said, rubbing the back of his head awkwardly. Shinobu and Gyomei both looked in his direction. From what his new friend had told him, the only ones who knew about Teiko were Shinobu, since she examined him regularly due to his Demon-eating, Gyomei, who trained him and allowed them to live with him, and the Master, who allowed Teiko to accompany her Older Brother, due to his unique method of fighting Demon's.
"Now that we are all here, we need to talk about the strange mark's a few of you have acquired" Amane began, two of her children sitting behind her. "Marks? Oh! Sorry, I didn't mean to interrupt Lady Amane" Tanjiro said apologetically. "It's perfectly fine Tanjiro. You have been unconscious since you left the Swordsmith Village, so you wouldn't know about this yet" Amane replied. "Tanjiro, when you were brought to the Butterfly Estate two months ago, your scar had transformed into a strange mark.
It had gotten larger, curling over your forehead like stylised flames. Over time the mark returned to the way it had been before, but during that whole time, you had a high fever. As the Mark regressed, your temperature went down. But I had to keep checking on you multiple times during the first few days" Shinobu explained. "I had no idea about that!" Tanjiro said in surprise, reaching up and touching his scar. "I noticed that my scar had changed over my initial two years of training.
It used to be a normal burn scar I got after I saved Takeo from getting burned by a falling stove when we were both younger" Tanjiro explained, patting the Demon boy in question on the head. "Well it definitely didn't look like a normal burn scar when we went on the Mission on the Mugen train!" The Flame Hashira confirmed. "So it changed after you reached a certain power level to what it is now, but what about the other state it was in? What caused that change? I assume it has something to do with Tanjiro's high temperature" Amane asked.
"When I was fighting Upper 4 in the Village, there was a point where it felt like my forehead was on fire. Then that burning sensation spread to the rest of my body, and I felt much stronger." Tanjiro explained. "So that was when your mark 'activated' so to speak. How much of a boost are we talking about here" Tengen asked. "Well, according to a Swordsmith boy I was with while fighting Upper Rank 5 in the Village, I gained a similar mark on my face, and I was able to easily behead the Demon" Muichiro added. "I also had a high temperature of over 39 degrees Celcius, and I believe my heartrate had surpassed 200 beats per minute" he added. "That would be fatal for the body" Shinobu said, worried.
"But it made him strong enough to kill Upper Rank 5 that easily" Tengen said, impressed. "Tokito has always been one of our strongest" Iguro said. "Also, another thing of note. During Tanjiro's battle against Upper 4's main body, his two youngest Brother's conquered the sun" Amane said. "So, the whole Demon family is immune to sunlight now then? That'll create a big problem for us" Sanemi said, crossing his arms. "Huh? Why is that?" Mitsuri asked. Upper 4 was still alive when the last of Kamado's family conquered the sun, so Muzan undoubtably knows about this now.
However, we are at a stalemate. Not only do the Demon's not know where our Headquarters are, but the Kamado's beat him badly when they first turned. They are all surely stronger now that they've had time to sleep, and learn to use their Blood Demon Art's with some mastery and not just instinct," Amane explained. "Kibutsuji knows the Kamado's nearly killed him the first time he confronted them as Demon's. And so he'll be both wary of moving to take them, and potentially reckless in doing so. This conflict of emotions is something we can exploit. Ever since young Shigeru and Rokuta have conquered the sun, Demon attacks have drastically decreased.
This will give us time to prepare, and train to increase the Corps overall power level," Amane said, "I will leave the decision of what to do next up to you, the Hashira" she finished, as she and her children bowed to them. The Hashira bowed back, "thank you Lady Amane" the Stone Hashira replied solemnly.
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The Kamado Demon's had since left the room to play together in the garden, Kie sitting beside her Son. "Muzan will definitely be coming after your family. Even with their defeat of him the first time, the temptation of so many Demon's who have conquered the sun would be too much to pass up" Shinobu said to Tanjiro. The oldest Kamado Son's look became dark. "I will not let him take my family from me. He's already harmed them far too much. If this mark can give me the strength to protect them from him, I'll do whatever it takes to master it!" Tanjiro said firmly.
"Before the training begins, I'd like to take some blood sample's from you Tanjiro. Something like the power this Mark gives is giving me Monkey's Paw vibes. That is to say, I'm worried it's causing more harm to your body than it is helping you" Shinobu said. Tanjiro looked at his Mother as she placed a hand on his cheek, staring at him with worry. He smiled at her, before turning back to the Insect Hashira, "of course. That sound's like a good idea" he replied.
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The family travelled back to the Butterfly Mansion, and the younger Demon's were happy to play with the three youngest Nurses under Nezuko and Aoi's watchful gazes. Kie and Takeo were adamant about sitting in with their Son/Older Brother while Shinobu took his blood. "Alright, and that should be enough. I'll take a look at this and let you know what I find Tanjiro" Shinobu said. Kie placed a hand on the teenager's shoulder and gave her a firm look, "tell me too" she said.
"Of course Mrs Kamado, I'll be sure to inform you both about the results" the black and purple-haired Hashira said with a smile. His Mother nodded, before they stood up to leave. "Thank you for this Shinobu. I don't want to worry my family if this Mark has bad consequences" Tanjiro said gratefully.
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Tanjiro sat at his desk with a piece of paper in front of him. He was trying to decide what his portion of the Hashira Training would be. He scratched his head, "it needs to be something that will increase the other Slayer's abilities. Maybe have them fight against my family? They're as strong as Upper Rank Demons, and can't be killed because they're immune to sunlight now. I know my family won't hurt them too much, so they can get some good training that way, but-" the Hashira sighed, that didn't feel right.
His family wouldn't want to hurt humans, and, even if they couldn't be killed, the thought of his Mother and Siblings being cut up for training horrified him. The teen groaned, leaning back in his seat. He had no good idea's!
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A few days later, Shinobu called him to see her at the Butterfly Estate. His family were sleeping soundly, so he headed over there by himself. The Insect Hashira turned to face him from her chair, "I have your test results here Tanjiro. Unfortunately it seems this Mark training might not be a viable idea" Shinobu said seriously. Tanjiro clenched his fist's, "why? Is something wrong with the Mark?" the Sun God Hashira asked. Shinobu stared at him, "it's true that while your Mark was active, you were much stronger, but I've compared a sample of your blood I took when you were first brought in, and the blood sample I took the previous time.
While your Mark active, your cells showed a high level of deterioration. The damage has since healed, but I believe that increased and prolonged use of the Mark will cause it to worsen" she explained. Seeing Tanjiro look confused by all the science talk, Shinobu sighed again, deeper this time with an exhausted look in her eyes, "it means if you keep using it, the Mark will kill you at a young age Tanjiro" she said sadly. Tanjiro froze, "how young?" he asked haltingly. "I don't know. I'd have to run more tests. As for everyone else getting the Mark, I believe we should hold off on the training until I can find out more" the other Hashira explained.
Tanjiro nodded, feeling numb. He wanted to live a long life with his family, and though he accepted that his life could be cut short in his Missions, this was something else. "Can you do anything?" the Kamado asked. "I can try. I might be able to find a way to halt the degradation of the Marked people's cells with more time. But for now, try not to stress too much, okay? Even if worst comes to worst, you still have time" Shinobu assured him gently. Tanjiro left the Butterfly Estate with a heavy mind and heart. What was he going to tell his Mother?
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Tanjiro spent the rest of that day in a daze. He knew he had to come up with a training regimen, but he couldn't focus his thoughts. He felt his thoughts swirl and fill his mind. He assumed that once all the Demon's were gone and his family were human again, he would be able to live a long life with them. At least he would do everything he could to live a long life, and not die to a Demon before that could happen. But he had no control over this. In exchange for strength to protect his family, he would leave them a lot sooner than expected.
How was he supposed to protect them if he died young? What should he do?! Tanjiro felt his breathing getting shorter as his thoughts and worries overwhelmed him. He tried to keep up his Total-Concentration and calm down, but his head pounded. Why couldn't he breathe? "Tanjiro! Tanjiro breathe!" Tanjiro heard his Mother's voice calling to him, but he couldn't tell what it was saying. "Tanjiro!" was her voice supposed to sound so far away? Why couldn't he take a breath? Darkness swam in from the edges of his vision, before Tanjiro finally passed out in Kie's arms.
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His eyes snapped open, to find himself staring up at the ceiling of his room in the Butterfly Estate. What had happened? Why was he in bed? Tanjiro wondered in confusion. "What?" he asked. "You, c-c-c- fell" Kie tried to say, and, unable to form the word she wanted, settled for another that conveyed the same thing. "Mom. I'm sorry, did I worry you?" Tanjiro asked. His Mother placed her clawed hand on the side of his face. "Stress?" she asked. Tanjiro frowned. She always seemed to know when anything was wrong with any of them, even without having his sense of smell.
The oldest Kamado Son sighed, "yeah. I am stressed Mom. I don't know what to do" he replied. "Sleep now. Then you'll feel better". "Maybe I'll have a rest. Okay?" Tanjiro agreed. So he went to lay down in his Futon, forcing his mind to quiet. 'I can't worry about that now. My family needs me!' Tanjiro thought, closing his eyes. He felt his Mother's claws gently moving through his hair. Slowly the teen fell asleep.