If someone were to ask him, Tanjirou would say that summer was the best summer he had had in a long time.

He had gotten used to spending quiet afternoons with Urokodaki, when he deemed it dangerous to train and spared Tanjirou the hottest hours of the day, noon and the early afternoon.

In those days, they would sit side by side, feet on the cold water of the river, and they'd bask in each other's company without a single word. Of course it was nothing like the Summers spent with his family, where they'd collect oranges and eat them with some ice, splashing in the water and making flower crowns to give their father, too sick to go himself, and their mother, who skipped meals to buy medicine instead.

This Summer though, this Summer was different from all the ones he had experienced before.

The days following Rengoku's death were marked by intense training and playful bickering. His words had not been carved on Tanjirou's mind only, but Inosuke and Zenitsu's too. Like a fire set alight on their hearts, not even Zenitsu complained about the conditions for their recovery and instead accepted them with nothing but a frown and a bitter expression, which was something tiny compared to his usual whining (he did complain when Tanjirou woke him up before sunrise, but he had to give Zenitsu the merit of following his lead and jogging alongside him every morning without fault).

The same fire didn't seem to appear in Aya, who had, although resuming eye training with her grandmother, completely forgotten about getting stronger. Instead she took on the position of the leader and tried to teach them about "repeating actions'' and what she had called "everything", but it was no use as no one could see how she did, so instead she tried to teach them more advance uses of Total Concentration Breathing and the healing Tanjirou had briefly learned from Rengoku. In exchange, Aya asked Zenitsu to teach her to be faster. It was the first time Tanjirou saw Zenitsu train with a girl in a decent manner, or Aya asking for help without a frown on her face.

Quickly enough, they were all catching up to her, and whenever Inosuke pointed it out, she just shrugged and congratulated them with a smile, this brought Tanjirou happiness, for some reason, but Inosuke instead was left dissatisfied over having lost a way to pick fights with her, which he said "was no fun".

Their second stay in the Butterfly Estate was more entertaining now because not only had Aya joined them in their daily activities and lunch breaks, but Yuu, who had at first seemed reluctant to even strike a conversation with them, made it a habit to join them from time to time. At this point, Tanjirou was able to call him a friend.

He spent a lot of time with Aoi and Shinobu now that he had officially joined the hospital wing. Whenever Yuu got close to Aoi, his cheeks would turn very red and he'd mumble and stutter, dropping all the syringes and the jars to the floor.

He'd call her "Aoi-senpai" with a blush on his cheeks and follow her around the Butterfly Estate like a love sick puppy, but Aoi paid him as much mind as she did any other resident in the Butterfly Estate, seeing Yuu more as a junior than as an equal. Then Yuu would go to Tanjirou and complain about the total indifference Aoi showed him in the romance department. Tanjirou would just pat his back and try to cheer him up with rice cookies or whatever the little girls offered them as a snack that day. Yuu would whimper over some sweet treats, which reminded him of Zenitsu, who seemed to spend a lot of time with him, tied together by their romance failures.

In regards to Inosuke… it could be said that Yuu didn't like him very much and Inosuke didn't seem to like him either. "He was bad with Yuno," Inosuke said, and even if Aya assured him it didn't matter, Inosuke was very stubborn. "He made you cry," when saying this, Aya stayed very still and thanked him silently, although she made him promise he wouldn't punch Yuu anymore.

However, it was more than Yuu's addition to their daily lives. The heavy atmosphere between him and Aya vanished as if it had never been there. What were harsh glances and bitter remarks before was now complete and total indifference if not for instances where they acknowledged each other in a friendly manner, peacefully cohabiting in the same room. This brought him immense joy.

Kaori and Kaede became a familiar presence to come across as they cooked in the kitchen or helped with daily chores. It was a pleasant surprise to find that Shinobu had offered them to stay permanently. In exchange for helping around the house and doing other work like official residents, she gave them their own rooms with a closet and some other furniture to keep their belongings, which weren't many, but Kaori expressed her gratitude at finally having some kind of privacy and at Shinobu's kind offer. Kaede only remarked, in a sarcastic manner, that it was nice to have somewhere to keep her cigarettes.

For some incomprehensible reason, Aya had protested this option, suddenly bursting into Shinobu's office and demanding the purpose of the offer. With a tight smile, the Insect Pillar had reminded her that she wasn't able to cover the costs of a house for three people with her current salary, and that they were only there because she had burnt down their home.

This served no use as Aya stubbornly insisted they moved out. However, when Shinobu mentioned that both her mother and grandmother had chosen to stay by their own will, and that they were not children, but adults she didn't need to take care of, she gave her a confused grimace and finally abandoned the topic.

Their confirmed stay was followed by countless and rigorous training sessions where Aya and Kanao fought against one another, now on equal terms. Tanjirou could see they were much more skillful than all the lower rank demon slayers who came into the estate, which led him to think that being trained by a pillar was fundamental on their chances for survival in the corps, and that in a few years of training, they'd be as quick and strong as Akaza and Rengoku had been on their battle to the death.

These sparring sessions had been a thing only they took part in, but these thoughts pushed Tanjirou to try and join them too, only to become stronger himself. Soon enough, all three of them, Aya, Tanjirou and Kanao were hopping around the training dojo in barely recognizable gusts of wind, being followed by Inosuke and Zenitsu, not wanting to be left behind.

Tag became, for the most part, their daily activity and entertainment.

Something that confused Tanjirou to no end was that, when she wasn't playing around with Inosuke or playing karuta cards with her family or Zenitsu, Aya spent long hours into the afternoon, by herself in the library.

He stared at the little pile of books by her side with titles such as "Molecular and Cell Biology of Pain", "Pain Research: Methods and Protocols" and "Advances in Pain Research and Therapy" and asked her what exactly she was reading for.

In response, Aya shrugged with a little smile and turned the page. "Just something I'm curious about."

"Why would you be curious about," he picked up a random book from the pile, "'The Clinical Biology of Aches and Pain'?"

"Nothing serious." She sat up and pointed to a kanji on the page, leaning the slightest bit on Tanjirou's chest. Her back was refreshing against her skin, despite it being 35 degrees outside. She read slowly and with difficulty, and he only then remembered that she mustn't have had any chance to read books in Himejima's house. "'Chronic... pain is experienced not only as... bodily discom... comfort? But also as fe-fears about the future, work impair...' Do you know how to read that word?"

Tanjirou looked at the kanji and thought really hard, but his attempts were futile. "Maybe you could ask Yuu?" She made a face to which he quickly added, "or Aoi might be able to help you too."

She perked up in interest but said nothing, Tanjirou never asked about her books again.

The next day he found Aya in the library, Aoi sitting beside her with a book of her own.

From time to time Aya would put the book down and chirp, "Aoi-senpai!", following Yuu's example, and pointing to something on the page. Aoi would tell her the meaning of the kanji, or sometimes read the entire sentence and explain it to her, and Aya's expression would light up.

"You're so smart, Aoi-senpai!"

"Am not, this is all basic stuff."

Aya would smile brighter and dismiss Aoi's comment. "Then you must be very good!"

No matter what she said, Aya found a way to compliment Aoi in everything she did. Eventually Aoi gave up and did nothing but frown when Aya commented how amazing she was, Tanjirou noticed that Aoi's smell started to turn sweeter.

Kanao would sometimes walk by and sit with them in silence, and the three of them would spend hours in a corner with the only occasional interruption of Aya asking Aoi something she didn't understand or Aoi saying dinner would be soon, but none of them made any effort on moving from their seats until it was Yuu who had to come get them when food was ready.

On the occasions Nezuko would come out of her box and not spend her time with Tanjirou she looked for Aya and sat on her lap. Those times Aya left the complicated biology books and picked up folks tales to read to Nezuko out loud, and all four girls leaned over the huge, illustrated book, to listen to Aya's voice, telling stories about journeys to the land of demons or shapeshifting foxes and spirits.

And when she wasn't with them, she dedicated her time to scribbling down countless letters addressed to strangers. Her crow took on the valiant task of sending all those letters in record time, which only made her write more, and so on.

It reached a point when Aya spent so much time in the library that her scent remained even when she was gone, and Tanjirou was unable to get in without blushing furiously.

Something he quickly realized was that she had never really gotten to know the residents of the Butterfly Estate on her first stay, as she was busier with training and her injuries (and she was ruder, too), so first impressions had been, if to choose a word, pretty horrible.

There was one time where him and Aya were walking to the kitchen together to join Zenitsu and Inosuke for lunch, talking about something trivial like their favourite food (Tanjirou mentioned that he liked mountain vegetables and she promised to cook them together one day) when suddenly the three little girls bumped into Aya when turning the corner.

The "go" board they were holding fell to the floor and all the pieces came spilling out, round black and white marbles shining against the wood. They knelt so quickly to pick them up from the floor that they didn't see it was Aya who they had bumped against, as she knelt to help them tidy up the little board game they saw her face and suddenly bowed.

"Miss Stone tsuguko, we hadn't seen you! Please forgive us!" Kiyo was the one to pledge, as both Sumi and Naho hid behind her back. Aya simply gave them a quizzical glance all the while Tanjirou picked up the remaining marbles from the floor.

"Why would you apologize?" She asked, tilting her head in a way Tanjirou thought was very cute.

Sumi gave a little shriek and Naho was the one to talk this time. The three of them were trembling. "You think it's not enough, do you!? We'll lick your shoes if that's what you want, or maybe clean your room!? Whatever punishment you think fit-"

Naho continued listing punishments, from brushing away the dust off her clothes to boiling agonically in excrement somewhere on Hell. Aya had stopped listening a while ago and was instead staring at the "go" board they were carrying.

"Are you gonna play?" she asked, making the three of them skip a bit on their feet.

After a few seconds of struggling, Sumi finally answered with a curt and fearful "yes!"

It took them all by surprise when Aya asked if she could play against them.

"Do you like playing?" Tanjirou inquired, following the little girls and Aya to somewhere in the garden where sunlight was abundant and the flowers' scent was strong.

"Yes, it's one of my favourite games," Aya smiled in contempt. "Since I was in bed most of the time, Yuu and I played a lot, you could say I'm quite experienced."

"It's been a while since I played," Tanjirou said. "My father used to try and teach me tricks and then see if I could beat him, but he died before I could."

Aya elbowed him on the stomach and gave him a smirk. "Then try and defeat me, little punk."

Tanjirou pointed at the three little girls that were already sitting at one end of the board. "Defeat them first," he hesitated a minute too long to be smooth, "brat."

Aya chuckled all the same and promised to do just that.

"Call me Aya!" She exclaimed when sitting at the other end of the board. The little girls squeaked, and then Aya proceeded to beat them ridiculously fast.

They placed once, twice, as many times as Naho, Kiyo and Sumi were willing to go in order to defend their pride.

Aya stared at them from the other side of the board trying to hide a smirk all the while the little girls whispered to one another, looking at Aya by the corner of their eye and talking about what they thought she'd do in her next move. Whatever they did, Aya was always able to overcome their tactics and rule the majority of the table with a handful of moves.

Tanjirou sat by their side and watched them play, and he was almost certain that Aya was going easy on them.

By the time they had played a bunch of times Zenitsu appeared, looking for his friends. When he found out Aya and the girls were playing "go", he demanded to play too.

"I can't defeat you on the battlefield, but I'll defeat you on the board!" He claimed, before completely losing to Aya.

Checking who could play the longest without losing to her soon became the real challenge of the competition, as it was clear as crystal that they wouldn't be able to defeat Aya's tactical abilities.

Kanao was the next one to walk by the little group that now took the entire corridor. Aya perked up at her sudden appearance and cheerfully suggested Kanao played too. The Flower Breathing tsuguko was defeated in a matter of seconds and Kanao was relegated to the end of the crowd of losers, who agglomerated around the board and stared intently at the game taking place.

"Aoi!" Sumi yelled, in a sudden moment of clarity. "She'll be able to win, I'm sure!" They turned the corner and disappeared in a flurry, as Aya stared at where their little heads had vanished with a little smile. A few minutes later, when Zenitsu was on his seventh loss, protests could be heard in the distance.

Aoi suddenly appeared, girls tugging her apron and urging the person they considered the smartest after Shinobu to help them defeat the villain.

And although she held her ground for more than any of them had been able to, Aoi too found her demise at the hands of Aya's careful stare and relaxed smile.

"That was fun," was the only thing she said, tidying up the pieces again before Aoi's shocked expression. Then Aya turned to Tanjirou. "Your turn."

He took a seat opposite her and everyone; Zenitsu, Aoi and Kanao, circled his form, as if cheering him on in a battle against a bear or a monster.

"You be careful, Tanjirou," Zenitsu hissed against his ear. "She will trick you if you aren't careful, that snake, I thought we were friends."

"We're still friends, Zenitsu," Aya said with a little chuckle.

"I'm only seeing a snake right now! A treacherous snake, I tell you!" He yelled back over Tanjirou's shoulder.

"He's bonkers but he's right, Tanjirou," Aoi stepped in this time, squinting at Aya from a more civilized position (sitting beside him instead of being on top of him). "Aya will definitely mess with your head and make you do what she wants you to do. It's like being a mouse in a labyrinth and she's the one guiding you to the cheese, but it's not cheese, it's a wrong move that will make her flip over the marbles and win."

"Aya is smart," Kanao only added. And making Kanao talk was impressive enough.

"You guys know I can hear you, right?" Aya said, tucking a strand of hair behind her ear.

"Shut up, snake," Zenitsu hissed menacingly behind Tanjirou.

"It's fine," he reassured the three of them. "I'll win against Aya for sure."

The little girls had changed sides and were now sitting on her knees, whispering into her ear. Aya argued in whispers too and Tanjirou could only guess she was both discussing moves and teaching them how to play.

At his words, they giggled and whispered something to Aya that made her entire face become a crimson red, which in turn only made the girls giggle more.

"Let's just play," Aya said, and the blush made her smirk quiver. "I want to see what you can do, eldest son."

"You were a worthy opponent," Tanjirou started, this time much more confident in his smoothness, "that's what I'll say when I beat you."

He made a move and the game started.

Tanjirou was quick, but Aya followed him at the same speed. They ended up placing one marble after another on an endless combination of snaps, like a dance that would not stop until the song came to an end.

"He's... winning," Aoi whispered, not even able to believe it herself. She was right, it turned out Tanjirou had either played as much "go" as Aya had or he was just smart enough to get on her level without the same amount of practice, because soon enough he started to corner Aya's white marbles with his black ones.

"Are you kidding me?" Zenitsu hissed, "I know I said you had to beat her but dude, I didn't think you'd stand a chance."

The rhythms of marbles being placed against the wooden board continued, but now Aya was frowning.

"Didn't expect any less from you," she said, quickly moving one marble in what Tanjirou knew was an attempt to distract him.

"I promised I'd beat you, didn't I?" Tanjirou said, with nearly half the board already marked by his black.

Aya only hummed, sweat on her temple, and tried to take over the board in a game no one won.

"Hey, I've been waiting for ages to have lunch, you assholes!"

"Inosuke!" Aya screamed. The little girls on her lap yelped when the body of their boar friend slammed against the board and completely destroyed their game.

"What the hell, dude!?" Zenitsu started. From his place on top of the board, Inosuke started taking fistfuls of the marbles into his hands.

"These things are shiny, can I keep them!?" He smiled with another cackle.

"You're unbelievable," Aoi said under her breath.

"It's not forbidden to throw yourself at the board, right?" Kanao pointed out. "Then does that mean Inosuke won the game of 'go'?"

The destroyer of their little game cackled on the floor, rolling around what little was left of the game. "I won, I won! I'm so smart, kneel before Inosuke, the lord of 'go'!"

Tanjirou smiled and patted his shoulder. "You won, Inosuke. Now help tidy up."

Inosuke laughed again and exclaimed "because you are all my underlings, I will!"

"I really wanted to play with you, I wish we hadn't been interrupted," Aya later told him, picking up the black marbles one by one and putting them on the little sack.

Tanjirou took the white ones and their hands brushed when he let them slide from his fingers and into the bag. "I wanted to play with you, too."

Aya smiled and pulled the string to close the bag.

"Oh, are you kids playing 'go'?" Shinobu's smile appeared by the doorway, looking at the mess left by Inosuke's little squabble.

"Yeah, have you played before, lady Shinobu?" Aya asked.

"I wouldn't say I've played, but I'm familiar with it," she offered Aya a sweet smile. "Do you want to play against me?"

Instead of Tanjirou, someone Aya could never, ever beat at 'go' was Shinobu.

July was followed by his birthday, which they celebrated with some cake. Inosuke brought him some shiny acorns, Zenitsu picked up a bouquet of wild flowers nearby and some sweets (that he had definitely stolen from the kitchen), Aoi baked him some cookies and finally, Nezuko took the effort to help Kanao make him a paper crane, which he left by his windowsill in the designated bed on the nursery.

He'd be lying if he said he didn't like Aya's present the most, who appeared at lunch holding a pot with mountain vegetables with a bright smile on her face and wished him happy birthday. It was followed by a terrible joke he had learnt to associate with her by now, but it was excusable, he thought.

Yuu would tell him it was her idea to celebrate his birthday in the first place, handing him a camera with a blank photo album. "So you don't forget you're alone."

The first picture Tanjirou took with it took the first page in its entirety, so every time he opened it he'd see the smiley faces of his friends.

So yes, if someone were to ask him, Tanjirou would say that this was his best Summer in a long while.

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