[Kimetsu no Yaiba] Du bist mein Herz

Title: Du bist mein Herz
Fandom: Kimetsu no Yaiba / Demon Slayer
Pairing: Rengoku Kyoujuro / Kamado Tanjirou
Words: 3.234
Completed: 2023/04/25
Summary: Shinjurou’s face goes through several shades of red and once even comes dangerously close to purple. His finger, still midair and pointing directly at Kyoujurou’s right ear, shakes in fury as the Hanafuda earring on his son’s ear playfully jingles to the mild spring breeze, almost as if it was mocking the oldest Rengoku.

“What the hell is that?!

“Hello Father, it’s good to see you too.”
Links: AO3 & FF.net

Shinjurou’s face goes through several shades of red and once even comes dangerously close to purple. His finger, still midair and pointing directly at Kyoujurou’s right ear, shakes in fury as the Hanafuda earring on his son’s ear playfully jingles to the mild spring breeze, almost as if it was mocking the oldest Rengoku.

“What the hell is that?!

“Hello Father, it’s good to see you too.”

Well, there goes any hope of delaying the inevitable. Kyoujurou has genuinely hoped his little brother would be the one to greet them, be it just so that Tanjirou could feel slightly more at home and won’t have to hide behind the Flame Hashira whilst he wishes to be anywhere else but here right now.

“I was made aware you have met Kamado already.” Kyoujurou sends a silent apology to the boy and swiftly pulls him to his side, an arm firmly resting around Tanjirou’s middle. He feels the boy relax ever so slightly and really, that is all Kyoujurou needs to hold his head high and stand strong.

“He is to be my Tsugoku. I believe Senjurou already informed you that we will be staying for a while.” Not that Kyoujurou has ever mentioned any names when he sent his crow to deliver the letter just a few short days ago, leaving his father blissfully unaware up until this very moment.

“I will never accept a descendant of the Sun Breathing Technique in my home!!” Shinjurou’s voice roars through the courtyard and in a fit of rage the man slams his bottle of sake to the ground, breaking the jar into many tiny pieces. At least neither Tanjirou nor he ended up as the target and Kyoujurou relaxes. He makes a mental note to help Senjurou clean the mess up later.

“Get him out of here, now!


“Well”, Rengoku begins once his father disappeared back into the house, both arms now tightly wrapped around his companion in a fashion that is most definitely not appropriate for a Master and his Tsugoku. “This could have gone a lot worse, don’t you think?”

“Rengoku-san…” A sigh. If he were able to, Tanjirou would probably massage his temples right now. “Your father hates me! He probably wants me dead!!”

The Flame Hashira chuckles and places a kiss on top of the boy’s forehead. “He will come around. He is a bit… hot-headed at times.”

“That’s certainly one way to put it…” The younger mumbles and leans into the touch as he distinctly recalls his previous encounter with the head of the Rengoku family: “In his defense, I called him a shitty old man and headbutted him unconscious. He might be a bit biased now because of this.”

Kyoujurou breaks out into laughter and squeezes the boy in his arms, basking in the warm feeling his partner ignites in him. His boy is without a doubt something else and oh, how he wishes he could have seen that in person.

“I’m so glad to have you at my side, my boy.”


Even now Kyoujurou vividly remembers the evening one sennight ago when Shinobu declared both of them healthy enough to resume their work; he had still been resting due to his injuries from the Mugen Train incident and Tanjirou had just completed his rehabilitation after waking up from his own coma.

(Those were two months of his life Rengoku never wants to relive again.)

The pair decided to spend one last evening together (or rather Rengoku was the one announcing it), sharing a couple of slices of Castella amongst themselves which the Kakushi were kind enough to gift them.

It should have been a joyous occasion, some quality time spent together before their inevitable departure (one Rengoku didn’t want to think about yet), however, tension hung in the air and Kyoujurou noticed early on that the boy was antsy, hands shaking like leaves in the stormy weather and eyes cast downwards. He wondered when the last time was that he saw these burgundy gems looking at him directly that day.

“Kamado boy.” Rengoku broke the silence and put the tray aside – the dessert had been left untouched anyway – and opened his arms in an invitation.

Tanjirou blinked and his brain hopelessly tried to process the scene in front of him. He glanced at his senior, then at the empty space separating them, and finally back at the Hashira.

Really, Kyoujurou mused, the boy was basically an open book right now and he could practically read his inner turmoil from his facial expression alone. Such a sweet boy, always too considerate of others and his surroundings, which is exactly why he was conflicted about the appropriate response to the current situation.

“Come here, my boy.”

All hesitation was gone, almost as if these words alone cut off all restraint holding him back, and Tanjirou was at Rengoku’s side in an instant, who in return wrapped his arm protectively around the boy’s shoulder, grasping it firmly and holding him close. Touches like these – a small brush of hands here, a squeeze on the shoulder there – had always come easy to them, so much so the line separating them in ranks had become blurry.

“What are you thinking about, my boy?”

“Come tomorrow… I won’t be able to see you again, right?”


Umu. We will most likely be sent on different missions. However!” The hand moved to Tanjirou’s head and ruffled his hair (it was so incredibly soft) “We are both members of the Demon Slayer Corps and share the same goal. Our paths are meant to cross again.”


Even an ordinary man could tell that the young slayer was not satisfied with the answer and in all honesty, Rengoku fully understood where the boy was coming from. He didn’t fare any better despite his words of encouragement. The mere thought that their paths would separate tomorrow made his chest ache. Even if their time spent together had been short, he had grown so used to the boy’s presence in his life that a small voice in the back of his head began to repeat the same desire over and over again. It was quite the ordinary wish, really, yet an impossible dream all the same.

“I know… I know I’m being selfish here.” Tanjirou’s voice was strangely calm and quiet. “But… I don’t want to part with Rengoku-san. Not tomorrow… or…” At this point his voice grew even smaller, “…any time… at all...”

Kyoujurou inhaled sharply and his heart was beating vigorously in his chest. Up until now, he had always avoided putting a label on this feeling, instead, he decided to stuff it away in the furthest corner of his heart and locked it up tightly. But there was no use running anymore, was there? Not with the boy so close to him and certainly not when they were wishing for the very same thing.

I want to stay by his side, Rengoku longed.
I want to keep him safe, he vowed.
I want—!


The boy beside him stiffened and held his breath in surprise. Oh, Kyoujurou realized, he had never actually called him by his first name before, had he?

“Won’t you become my—” He stopped. ‘My what’ exactly? They were both Demon Slayers, Hashira and Kanoe respectively, and depending on their mission they oftentimes won’t even know if they would live to see the next sunrise.

It was selfish.
Utterly and completely selfish.

And yet…
And yet—!


No, this won’t do at all.

“Tanjirou, my boy.” Kyoujurou threw caution to the wind and cupped the boy’s face in his hands. The reaction was immediate; soft cheeks grew rosy and began to warm up under his fingers. Tanjirou opened and closed his mouth repeatedly, each time without uttering as much as a sound for he was too stunned to talk.

“When we first met I wronged you and your sister in many ways. I am utterly ashamed of myself to have called for your executions.” Tanjirou shook his head as much as possible and wanted to argue, wanted to say there was nothing to apologize for, however, the Flame Hashira didn’t give him the chance to interrupt him. “But you proved me wrong. Your sister fought bravely to protect the passengers on the train. This mission – fighting alongside you and protecting you – has been my greatest honor as a swordsman. On that day so long ago I was willing to lay down my life, not only to protect all these innocent people with us but first and foremost to protect you, my boy.”

Rengoku felt Tanjirou’s lips quiver under his thumbs and soon the first tears brushed his fingers. He really has done it now and made his boy cry again, hasn’t he? Kyoujurou carefully closed the short distance separating them, with his eyes he was seeking permission and – oh, his heart skipped a beat once he saw the faint nod – tenderly kissed the tears away one by one, trying all in his might to ebb their flow, but more kept on coming.

“Re-Rengoku-san is so mean…” Tanjirou hiccuped and tried in a feeble attempt to get his tears under control. “Y-you need to be safe, too! That day… I wanted to fight with you so badly. I keep thinking if only I had been able to push myself just one more time… just one more Hinokami Kagura to keep me moving… then maybe… maybe–!!”

Perhaps things would have gone differently on that day, Kyoujurou suspected, nevertheless, he stood by the decision he made back then. Maybe he would have gotten away with less life-threatening injuries if the boy had miraculously intervened, but at what cost?

(Kyoujurou could have lost him that day.)

(Tanjirou did almost lose him.)

“And I’m glad you honored my order, my boy. Knowing you were safe kept me going and pulled me through the battle.”

“NO!” He shook his head violently. “No, I don’t… I don’t want that if… if…” Tanjirou grew more and more frustrated with himself. Why was it so difficult to put his feelings into words? In his mind he knew exactly what he wanted to say, so why was his mouth not cooperating?
“I just…” Tanjirou closed his eyes and practically shouted the next words: “I just don’t want to lose you again!!”

And that was just it, wasn’t it?
They were both selfish, longing for the same impossible dream.

“Tanjirou.” Impossible, yet worth fighting for. “One might say I lost too much on that day. My eyesight, for one, was significantly affected and even now that my body is considered more or less healed, things will never be the same for me as they were before. However! I gained something much more important and precious. Tanjirou”, he paused for a second and gathered the courage to ask the following question: “Will you do me the honor and be my partner in life?”

Later, when all was said and done and every last tear dried up, Kyoujurou will think back to this very moment with the knowledge that he broke Tanjirou’s brain just a tiny little bit.

“Y-y-you…” The boy’s face turned an impossible shade of red and his mouth hung wide open. “You… you really mean it?” Tanjirou was so valuable right now. Both were, Kyoujurou suddenly realized and blinked away his own tears that were burning in the corner of his eyes. When was the last time he had cried? Oh my boy, if only you realize what you’re doing to me, Rengoku mused and softly rested his forehead on Tanjirou’s.

“Ah, my boy.”


“Call me by my name, Tanjirou.”

“…Kyou…..” He hesitated, bashful. “Kyoujurou-san…?”

“Umu.” A kiss on his left temple.


“Umu.” And another one to his right temple and finally, finally a giggle escaped the boy and oh, wasn’t that the sweetest melody Rengoku has ever heard?

“Do you…” Tanjirou sniffed and dried the last remaining tears with his sleeve. “Do you still have the earring?”

Of course, he wanted to scream, as if he could ever lose one of his most cherished treasures.

“I do, my boy.” The blond fished the jewelry out of his sleeve and presented it to the boy; it was one of Tanjirou’s Hanafuda earrings, which as a matter of fact was currently missing on his left ear.

People might call Kyoujurou a romantic idiot (his father certainly would), but nothing and nobody for that matter would ever be able to stop him from believing that the same earring he was now holding in his hand had indeed called him back to life. On the day he opened his eyes for the very first time since what became known as the Mugen Train incident, his right hand felt different. Once the first layers of confusion and drowsiness were gone, he lifted his arm and noticed the talisman in his hands. It took his puzzled brain a moment or two to connect the dots, but when the realization hit him the poor man was left even more dumbfounded than before. It wasn’t until much later when Kochou told him the wearer of said earring was currently on a mission, one he had to be dragged away from apparently, since the boy refused vehemently to leave Rengoku’s side. He had to, however, as work needed to be prioritized, so wonderful and brilliant Tanjirou came up with the idea to leave one of his heirlooms behind with him.
Waiting for the boy’s return was unbearable, to say the least, and once he heard of the boy’s injuries his world came crashing down all at once. Since then Kyoujurou had been holding onto the boy’s heirloom and praying for his recovery.

“Thank you for keeping it safe”, Tanjirou smiled and took off his remaining earring before he leaned into the Hashira’s right side. “May I?” He asked, voice barely about a whisper.

Rengoku nodded, not trusting his own voice.

“The thought of losing you… it scares me so much.” Tanjirou brushed a handful of Rengoku’s bushy hair back (it really felt soft and fluffy; he could easily get lost petting it all day long if he was honest) and his fingers grazed the Hashira’s ear. Rengoku shivered in anticipation.

“I want to believe in a future without demons. In a future where Nezuko is once again human and lives the life she dreams of. A future…” Tanjirou leaned back, gone was the earring from his hand. “A future where we can grow old together.”

For a moment Kyoujurou forgot how to breathe. His hands – now shaking much worse than Tanjirou’s did before – moved to his right ear and his eyes widened once they felt the piece of jewelry out.

“Tanjirou, y-you…?”

Please, Kyoujurou-san.”

It was both a request and a permission.



My boy.” Tanjirou nodded and shifted to his right side, granting the Hashira easier access to his left ear, where the said man placed a kiss and a small yelp escaped Tanjirou’s mouth. “Your words are still burnt into my memory. It’s Rengoku-san’s victory, you said, and even dared to call an Upper Moon a coward.” He chuckled as he remembered the next part clearly. “I certainly couldn’t believe my eyes when you threw your Nichirin Blade after the demon. You truly astonished me, my boy.”
“Now you’re just teasing me!” Tanjirou whined and hid his face in the palm of his hands. His blush reached the tip of his ears though, which amused Kyoujurou tremendously. He couldn’t help but softly snickered at the boy’s adorableness and finished placing the earring on his lover’s ear. “Your feelings and your passion resonated within me on that day. You, my boy, set my heart ablaze.”

“….s’not fair.” The voice was muffled and Tanjirou’s shoulders shook rapidly, yet he still vehemently refused to show his face.

“Are you crying again?” The Hashira asked, a hint of amusement mixed in his voice.

“N-no.” Tanjirou sniffed very obviously crying. Two strong arms embraced him and in one swift motion, he found himself in Kyoujurous’s lap. Gently, almost as if he was afraid to hurt the boy, he peeled off the hands covering Tanjirou’s face and revealed reddened eyes and a runny nose. Nothing about this image screamed breathtaking, yet Rengoku’s heart was running a marathon in his chest.

“Can I kiss you?”


When their lips touched it neither ignited explosions nor the grand fireworks poets like to write about. By all accounts, the kiss was a very chaste matter yet at the same time it was perfect.

It was them.
It was home.

“My boy?”


“Does that make me your husband now?”


Tanjioru spluttered a string of incoherent words, unable to form any complaints or arguments and finally (albeit reluctantly) surrendered to the inevitable and hid his flushed face in his lover’s chest, lamenting very loudly about the fact of how mean Rengoku was to him.

Kyoujurou promised him many kisses to make it up.


“Aniue, Tanjirou-san.” The voice of his little brother brings Kyoujurou back to reality. In the blink of an eye, the small figure tackle-hugs him and presses his face into Kyoujurou’s chest. Rengoku’s confusion soon melts and gives way to a bright smile and he embraces his little brother.
“I’m home, Senjurou.”

Once Senjurou calms down and apologizes to Tanjirou (he is genuinely embarrassed to have ignored the young Slayer) he ushers the two guests inside and quickly offers them tea and some sweets he has prepared beforehand.

“Both of you please rest up.” His eyes fall on Tanjirou and he smiles politely, even if a little awkwardly. “I hope you don’t take Father’s words to heart. He just needs some time to warm up.”

Well, Tanjirou thinks with his head hanging down, in my case, he might as well need a lot of time.

“I will get the guest room ready in the meantime.” Senjurou bows and wants to stand up, but Kyoujurou stops him in his tracks. “Stay with us, Senjurou!” He pats the empty space next to him. “There won’t be a need for a guest room anyway, a second futon in my room is more than sufficient.”
“Ren-Rengoku-san!!!” Tanjirou screams appalled and smacks the shoulder of his partner, almost as if he is scolding the man to behave in front of the child.

Senjurou’s cheeks turn pinkish and he casts his eyes downwards. Even someone as young and innocent as he is understands the implications of this statement.

“I understand, I’ll get another futon ready for your room then, Aniue.” The youngest Rengoku turns to Tanjirou and bows deeply. “Please take care of my brother, Tanjirou-san.”

“I’m not—I mean we’re—arGH!!” The young Demon Slayer gives up and hides his face in the nook of Kyoujurou’s neck, cheeks all puffy and aflush.

“You’re a bully, Kyoujurou-san”, he mumbles just loud enough for the man in question to hear him and Rengoku chuckles, his next words are spoken in a low and hushed voice and clearly not meant for a child to hear. It is at this moment that Senjurou decides to give the couple some space and quietly exits the room. His big brother is back, healthy and full of energy on top of it, and with the new addition of Tanjirou as his brother’s Tsugoku things were about to get lively in the Rengoku Estate.

Senjurou smiles thinking about the future.

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