A/N: I honestly still have a chapter to update for my Fairy Tail fanfic, but I couldn't get this idea off of my head, lol.

Disclaimer: I don't own Kuroko no Basuke, Katekyo Hitman Reborn, and their respective characters. I only own this fanfic idea. HOWEVER, if there has already been a similar fanfic before, I'm sorry but I was not aware.

1.

"I'm sorry, Setsu, but I can't be your light anymore."

The words still hurt, if she were being perfectly honest, but how could they not make her heart throb painfully whenever she recalled how defeated Daiki had looked, how he had just accepted it as fact. She wished she could ask him to try harder, but she knew that he had tried his hardest to retain that sense of teamwork that had been ruined by his sudden growth in abilities; he had tried his best, unlike the rest of the Generation of Miracles, who didn't seem to find the lack of teamwork disturbing.

Her fingers tightened on the metal pole adjacent to the doors of the train. She could hear the PA system announce that the train was nearing Namimori, her temporary home for the summer (or was it just a place for her to escape the cold gymnasium where the coaches had them run teamwork drills that they weren't putting any effort into? Or maybe it was to convince herself that everything was fine right now and what had happened was just a bad dream she would wake up from once she returned to Tokyo.).

It wasn't a trip she had planned. It was actually her mother who had encouraged her to go to quaint Namimori. Setsuna probably wouldn't have ventured to this small town if it weren't for the fact that her mother's sister, a Sawada Nana, lived here with her son, Tsunayoshi. Sen, Setsuna's mother, had told her that she hadn't kept in contact with her sister, and Setsuna understood that it was because of how busy Sen was with her job as a CEO to a fashion and design company. (That and Nana didn't seem to reply to letters she had sent, so Sen hadn't felt like taking the initiative to contact her sister anymore.) It seemed that when Sen had noticed how down Setsuna had been lately, it had given Sen a reason to try and contact Nana again, and it paid off. Setsuna could remember hearing how happy her mother was to finally be able to talk to her older sister.

The train started to slow down, letting out a screeching sound before announcing that they had arrived at Namimori. Setsuna was pulled away from her musings as she grabbed the handle of her sky blue luggage bag and stepped out of the train.

"Ah, Kuroko Setsuna-chan?"

She blinked in surprise, wondering how anyone had noticed her. A few steps away from her stood a boy with brown, gravity-defying hair. He was definitely a few inches taller than her.

"Yes?" She wondered who the boy was.

"I'm Tsuna. Sawada Tsunayoshi? I'm your cousin," he said sheepishly. "I thought Kaa-san would have told you or Sen-oba-san. Kaa-san couldn't make it since she had to help Lambo, ah, one of the kids at home. He accidentally made a mess in the kitchen, and no one else was there to help clean it up, so she sent me to go instead. HIEE! I'm rambling, I'm sorry!"

Had she been another person, she probably would have been annoyed by it, but Setsuna found her cousin's rambling endearing. She also probably wouldn't have believed his claim of being her cousin so easily, but she could see his resemblance to her Nana-oba-san; her mother had shown her a picture of the woman, but had forgotten to show her a picture of Tsuna.

"It's alright, Tsuna-kun," she gave him a gentle smile. "Please take care of me."

Tsuna just let out a chuckle before holding out a hand. "Would you like me to take your luggage?"

Setsuna was about to politely decline before she felt her shoulders aching slightly. Aside from the luggage, she had brought a backpack with her and had filled it to the brim with books to read so she wouldn't be bored. She probably shouldn't have that much, but reading was something she enjoyed (and it helped her forget about the bad things). So, instead, she gave her cousin a smile and let him take the luggage from her. "Thank you, Tsuna-kun. And you may call me Setsuna. We're cousins, after all."

"Of course, Setsuna-chan," was directed her way with a bright smile before they made their way up.

It was strange to be led into a limousine. Setsuna couldn't recall her mother mentioning that the Sawadas were rich. As she turned to look at Tsuna with a questioning gaze, he laughed awkwardly.

"Sorry, about this. I guess I forgot to tell some members of the family to go about this normally," he said, and she wondered about his emphasis on the word 'family' as he opened the door for her.

She went inside and Tsuna closed the door for her, walking over to the other side of the limousine to sit next to her. He looked forward to the driver's seat, where a man with a pompadour hat sat comfortably at the wheel.

"Tetsuya-san, did Reborn make you do this?" her cousin asked.

The aforementioned Tetsuya-san chuckled. "I'm afraid so. He did tag along, though."

"HIEEE?!" Tsuna screeched, directing a glare towards the area beside Tetsuya.

It turned out that there was another man sitting there. He had peculiar-looking sideburns and he was wearing a suit and a fedora. "As your advisor, Dame-Tsuna, it's only right to ensure your and your cousin's safety."

"We're in Namimori! Nothing's going to happen."

"I do seem to recall many things happening in Namimori."

"That was before! Don't drag Setsuna-chan into this, Reborn."

"Drag me into what exactly?" The teal haired girl had remained quiet throughout the exchanges, comfortable in just watching Tsuna interact with the odd fellows in the limousine. She didn't think they were dangerous; if Tsuna was at ease with them, despite his slight irritation towards the man called Reborn, then that meant they were safe to be around. Still, when she heard her name brought up into the conversation, she couldn't keep her silence.

"You must be Kuroko Setsuna, then? I'm Reborn. I'm Dame-Tsuna's tutor and advisor."

Reborn's words confused her, though. Weren't tutor and advisor the same things? He was there to teach and guide Tsuna. Why the distinction? Or am I overthinking this? "…Right. It's nice to meet you, Reborn-san, but you haven't answered my question."

She didn't notice Reborn glancing at Tsuna before replying with, "Into your cousin's exploits."

"I see." No one seemed to be willing to elaborate further, so she took the answer as it was.

Tetsuya began to drive. Setsuna looked out the window and noticed how peaceful Namimori was. She could tell that it was going to be very different from Tokyo, where she was used to the hustle and bustle in the city. At least, she thought, I won't have to see Daiki and the others yet.

She sighed before resting her head against the window and closing her eyes.

When he noticed that his cousin had fallen asleep, Tsuna directed a glare at Reborn. "I only just met her, Reborn. I'm not about to drag her into the Famiglia."

"She won't be able to escape from the Mafia now that she's staying with you and your mother," Reborn argued back. "If a spy or any other hitman were to see her with you, they could easily use her as leverage. It would be better to make her aware of the potential dangers of staying here, so that she could learn to defend herself, too."

"I know, Reborn," Tsuna eventually sighed, "but… seventeen years of my life I went by knowing I had a cousin in Tokyo, but never being able to meet her because of the loss of contact between our mothers, and then because of the Mafia's intrusion in my life. I just want to be a normal cousin to her for a while. I know I'll have to tell her. I mean, she's staying here for more than a month, kami knows what could happen. But…"

"A few days, Dame-Tsuna," Reborn told him, lips pressed together in a thin line. "You can give her a sense of normalcy for a few days before you have to tell her. We're not breaking Omerta, after all. She's your cousin, and though she's not a direct descendant of Primo, she's still a relative, and thus, could be used as a hostage."

Tsuna sighed again but nodded.

"As for the loss of contact between Mama and Kuroko Sen," Reborn started, eyes narrowing in suspicion, "how did that come about?"

Tsuna's eyebrow raised at the question, but his Intuition was also telling him that something had seemed off about the whole thing. "Kaa-san's the older sister of Sen-oba-san, but they weren't very close. Kaa-san said she and Sen-oba-san used to write letters to each other once a month until Sen-oba-san's letters stopped coming. Kaa-san kept writing for a year before she gave up and thought her sister didn't want to talk to her. Imagine her surprise when Sen-oba-san sent a letter again. Maybe the post just got mixed up?"

But even Reborn knew that Tsuna had just wanted to be hopeful. Tsuna didn't want to think that some enemy Famiglia had actually known about the Kurokos and had cut off communication with the Sawadas on purpose.

"I think you already have your own thoughts on that, Dame-Tsuna."

When Setsuna woke up, the car had just stopped into a modest, two-story house with a cute front yard. "We're here?"

"Yeah," Tsuna replied with a small smile. "Must've been tired from the travel, huh?"

"Just a little," Setsuna responded. "I never had much reason to travel out of Tokyo before."

Tsuna hummed at that and helped her with her luggage, taking it in her hands again. "Kaa-san's probably making dinner right now. You can settle in to your room first before I introduce you to the kids."

"Kids?"

"Ah, Lambo and I-pin. They're like my younger siblings."

Adopted, then, Setsuna mused as she walked towards the driver's seat and knocked on the window. The window rolled down and Tetsuya looked at her curiously.

"Did you need something, Kuroko-san?"

"Ah, no, I just wanted to thank you for driving us. I hope I didn't inconvenience you."

"It wasn't an inconvenience at all, Kuroko-san," Tetsuya smiled at her before rolling up the window. After Reborn had exited the car, Tetsuya drove off.

Setsuna then began to follow Tsuna and his tutor inside the house, where the delicious smell of hamburger steak wafted throughout the house. She could also hear childish arguments coming from equally childish voices. She took a small peek in one of the rooms, which turned out to be the kitchen, and she saw a small boy with an afro wearing a cowsuit laughing at a Chinese girl in a red qipao.

"That's Lambo and that's I-pin," Tsuna told her, pointing at the afro boy and the Chinese girl respectively. "Let's head up to your room first."

She followed him to the second floor and went past one door on her right before Tsuna opened the door next to it. Inside was a room with lavender colored walls. The bed had white sheets. Right next to the bed was a window decorated with orchid colored curtains. Directly under the window was a medium-sized white desk with a white rolling desk chair. On the other side of the bed was a bookshelf, and in front of the bed was a row of three cabinets.

"The room is beautiful, Tsuna-kun," Setsuna told him as she took her luggage from him.

"Kaa-san will be happy to know that. She decorated it for you once she was told you really were coming. She always wanted a daughter," Tsuna chuckled. "I'll leave you to your packing. When you're done, just come down to to the living room. It's on the other side of the stairs."

"Alright," and with that, Tsuna left her to do her unpacking.

Setsuna easily hung her clothes inside of the cabinets, which were quite spacious and were also lined with small cubby holes to place folded clothes in. She also placed her books on the bookshelf, assorting them from left to right based on what she would be reading first. She then freshened up and changed into a simple, white summer dress before heading downstairs.

When she arrived, the children weren't arguing anymore, and were instead playing with some Lego. Tsuna, upon noticing her arrival, quickly called the kids over.

"Lambo, I-pin, I want you to meet Kuroko Setsuna-chan. She's my cousin. Treat her well, okay?"

At his words, the two children curiously looked at Setsuna. It was I-pin who first approached her and held her hand, saying, "Setsuna-onee-san?"

Setsuna was surprised at how she had been quickly accepted by I-pin, and after glancing at Tsuna, who gave her an encouraging nod, she smiled at I-pin. "Yes. It's nice to meet you, I-pin-chan."

"I'm Lambo-sama! You can be my other slave!" Lambo cheered before Setsuna smiled at him, too.

"I'm afraid I won't be a very good slave, Lambo. Perhaps we can be partners-in-crime, instead?"

Lambo seemed to consider her words before nodding. "Okay. Setsuna-nee can be Lambo-sama's accomplice."

Before the kids could rope her into playing with them, Tsuna had quickly excused both himself and Setsuna so that he could introduce her to Nana. Setsuna followed Tsuna to the kitchen, where she saw the woman in the pictures her mother had shown to her.

The pictures didn't do her justice.

Sawada Nana was beautiful. Her hair was perfectly in place, tied neatly into a bun. Her warm brown eyes were inviting and her smile was very gentle. She reminded Setsuna of Sen.

"Ara, is this Setsuna-chan?" Nana smiled as she lowered the heat on the stove and approached the girl, who she quickly enveloped into a hug. "It's so nice to finally meet you."

"It's nice to meet you, too, Nana-oba-san," Setsuna said shyly. "Thank you for letting me stay here."

"Don't worry about that, Setsuna-chan!" Nana giggled. "I would love to get to know my niece, and I might even let Tsu-kun stay over at your place next time."

Setsuna liked how accepting Nana was. They had just met but the woman had already treated her as if they had known each other for years, and Setsuna liked that she was starting to become comfortable in Namimori. She had worried that Nana would have been inconvenienced by her at some point, but the woman seemed like the type to take care of those under her care.

Setsuna decided that she liked her aunt.

"Let's go eat now, hmm? Tsu-kun, could you set the table for me, please?" Nana told her son before returning to what she had been cooking.

"Hai," was Tsuna's answer as he started getting plates and utensils for everyone.

Setsuna hurried over and took some of the utensils from Tsuna. "I'll help."

Tsuna graced her with a thankful smile as they began to quietly set the table.

I could get used to life here, Setsuna mused as everyone gathered around the table to eat.

A/N: I really hope I got the characters' personalities correctly :c Setsuna, though, won't really act like the male Kuroko. She'd still be quiet and polite, though, but I'd like to think that Setsuna would still be the type to speak her mind, especially when it came to concerns involving her. I'd also like Setsuna to be a little more confident about herself. AND please don't be afraid to point out any errors I may have made (just please don't be rude about it lmao).

Cover photo from: reborn . fandom wiki/ Takeshi_Yamamoto

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A/N (June 10): I initially made an error when I posted this chapter. I said that Setsuna was a descendant of Primo, lmao, my mistake. She's not, since she's related to Tsuna through Nana, not Iemitsu. Thank you, Lynchin, for pointing out my mistake.

Possible FAQs

1. What exactly is the timeline of this story? In this story, the Representative Battle of the Rainbow is done. Tsuna's about to start his first year in high school. As for Setsuna, she's just finished Teiko and is about to start in Seirin after the summer. I'm not sure how Japanese schools work exactly, but I'd like to pattern it after what I know (school year starting after summer).

2. Why 'Setsuna'? I didn't want Kuroko Tetsuya's female version to still have a 'Tetsu' in the name, and I think Setsuna is a pretty name. PLUS, it totally fits with how she and Tsuna are cousins, since they'd both have 'tsu' in it. Furthermore, Kusakabe Tetsuya. I wouldn't want to confuse the 'Tetsu' in their names.

3. Why is Tsuna acting casually with Setsuna? I'd like to think his Intuition is telling him it's okay to do so, although I'll probably tackle this in the next chapter. Plus, it's a relative he hasn't met before. He may have been a shy middle schooler, but Tsuna in this fic is more confident.

4. Why Yamamoto Takeshi? I always thought that a female Kuroko would probably go well with someone calm but passionate about their sport: like Yamamoto Takeshi. He'd also be cheerful enough to counter Setsu's stoicism.

5. Will this follow the Kuroko no Basuke timeline? Most likely, yes, but I'm going to be prioritizing Setsuna's relationships with the Vongola Famiglia's members since she's going to be staying with the Sawadas for around 40 days (since, according to Google, summer breaks in Japan typically last that long).

6. History between Aomine and Kuroko? Yes, they had some history, but all will be explained in due time.

7. Will anyone from Vongola attend Seirin? Still wondering about this but probably not.

8. Will Setsuna have Flames? Yes, but I'm not telling yet hehe. She will have a secondary Flame, though.

9. How often will I update this? That is a question I can't answer since I write when I have the time + motivation to write, but to be safe, expect slow updates, like once a month.