When Ruby got the first text from Ria, she was in the middle of preparing snacks for Hanamaru and Yoshiko. The redhead's family was out for the night, her parents on an anniversary trip and Dia staying over at Mari's, so the trio of first years decided to have a sleepover. When Ruby had questioned her sister on why they didn't just have one big sleepover at their place, Dia had gone red for a while before sputtering something out about Mari wanting to give her something, which was a euphemism that went right over Ruby's head.

After making sure the tea was steeping properly, Ruby checked her phone.

RiaRia: Hey, can I ask you a personal question?

Ganbaruby: Sure. What is it?

RiaRia: So... how do you tell someone you like them? Romantically?

Ganbaruby: ...where is this going, my purely platonic friend?

RiaRia: It's not you! Don't make this weird! It's... someone I've known for a while.

Ganbaruby: Oh! You're in love with Seira-san!

RiaRia: WHAAAAAAAT?! HOW DID YOU COME TO THAT HALF-BAKED CONCLUSION?!

Ganbaruby: You... don't really have many friends, so if it's not me then your sister is basically the only possibility.

RiaRia: It could be some other family member you don't know about!

Ganbaruby: ...I thought you didn't want to make this weird.

RiaRia: ...just help me.

Ruby thought to herself. "Hmm... what would onee-chan say?" she mused aloud.

A small Chibi-Dia appeared on her shoulder, ready to dispense her sagely, sisterly advice. "I will not tolerate such notions! It's far too soon for you to consider such things!" she said sternly.

Ruby frowned. That was remarkably unhelpful. "Um... What about Kanan-chan?"

Chibi-Kanan wasn't much better. "You're asking me? Oh boy, I don't know... Maybe go diving together?"

"Hmm. How about Mari-chan? She should have some good advice."

"Shiny!" cheered Chibi-Mari as she poofed into existence. "So dear little Ruby-chan is asking for love advice?" She giggled. "Alright! If you wanna get laid, you have to-MMPH!"

The redhead sweatdropped as Chibi-Mari was tackled by Chibi-Dia, the former flailing wildly as the latter tried desperately to muffle her words, all the while shouting about how she would not have her sister's innocence corrupted. Chibi-Kanan chased after the pair helplessly, eventually getting caught up and dragged into their scuffle, the trio somehow falling into a cartoon cloud of smoke that orbited Ruby's head.

"...I suppose I should have seen that coming," sighed Ruby in resignation. "Chika-chan?"

"Give her a mikan!" cried Chibi-Chika as she materialized atop a large mikan. Upon noticing the large mikan, her face formed an expression of awed delight. "Sweet!" she enthused as she tried to pry open the rind to get to the juicy fruit beneath.

"...You-chan?"

"If I knew how to do that, I'd already be with Chika-chan," said Chibi-You sadly. For some reason, Chibi-You was dressed in her Uchicchi costume, and the brunette stared longingly at Chibi-Chika before placing the mascot head atop her own.

"Poor You-chan," sympathized Ruby. "Ganbaruby!" Chibi-Uchicchi saluted Ruby in acknowledgement before returning to staring longingly at Chibi-Chika. "Maybe Riko-chan can offer some city girl wisdom."

As soon as she appeared, Chibi-Riko began spewing a crimson fountain from her nose. "It's genuine sisterly incest!" she cried in bliss as she became lost in fantasy. She eventually passed out in Chibi-Uchicchi's arms.

Ruby sighed. Her senpai were of absolutely no help whatsoever. Well, Chibi-Mari might be, but Chibi-Dia would never let her get a word in. Disappointed that she didn't know how to help her friend, Ruby texted back a final message.

Ganbaruby: I'm sorry Ria-chan, but I don't know. I have to go for now, but I'll sleep on it. Maybe I'll have something tomorrow.

RiaRia: Thanks anyway. Good night.

With that, Ruby gathered up the serving tray laden with tea and snacks and walked to her room, leaving the six Chibi-Senpai behind.

When she got there, she was met with a surprising sight.

"Hanamaru-chan?! Yoshiko-chan?! Why are you both in your underwear?!" squeaked the reddening hostess.

"Yoshiko-chan and I had something we wanted to ask you, zura," explained Hanamaru with a smile. Beside her, a blushing Yoshiko nodded in agreement. The brunette turned to her partner. "Go ahead, Yoshiko-chan," she prompted.

"EHHHH?! You're leaving this to me?!" cried the fallen angel. Hanamaru replied with a serene nod. "Y-Y-You just want me to get all worked up and embarrassed because you think it's amusing," accused the blunette.

"Yoshiko-chan," said Hanamaru forcefully, smile still in place.

The blunette turned away, grumbling under her breath about temptresses and succubi, before looking at Ruby. She gulped. "R-Ruby, Hanamaru and I think... well, we'd like it if... that is, we both had the idea..." Several more seconds of nigh incoherent stuttering later, she all but smashed her blushing face into her hands in embarrassment, too mortified to go on.

Hanamaru looked on in satisfied mischief before intervening. "What she means, is that both Yoshiko-chan and I would like to invite you to form a polyamorous relationship with us, zura."

Ruby blinked. "Um... what do you do in a polyamorous relationship?" she asked innocently.

"We'd hold hands while walking to school, spend our free days together on group dates, cuddle up with each other during sleepovers, and love each other zura," explained Hanamaru patiently. Next to her, Yoshiko nodded shyly.

"Don't we already do those things now?" pondered Ruby.

"Hmm. Maybe we're already in a polyamorous relationship and we just didn't know it zura?" mused the brunette.

"Can we please change into some proper clothes now?!" exclaimed Yoshiko suddenly as she tried to cover her nearly naked body.

One Scene Transition Later...

"So wait," asked Ruby. "Why were the two of you in your underwear?"

"Zuramaru thought it would increase the likelihood of you accepting," explained Yoshiko, no longer embarrassed.

"I read about it in the book Riko-san lent me, zura!" added Hanamaru. "The protagonists take their clothes off and confess their love for each other. Then they go to sleep together, zura."

Ruby nodded in acknowledgement. "I suppose that makes sense," she said.

Yoshiko sighed. "They're so innocent..." she muttered under her breath.

"So? Will you accept zura?" prompted Hanamaru expectantly.

The redhead nodded. "I'll do it," she declared.

"Hooray zura!" cheered Hanamaru. She jumped on Ruby's bed. "Cuddle pile!"

And so, the three girls spent their sleepover enjoying each other's company, occasionally testing the boundaries of their newfound relationship with chaste kisses on the cheek. They fell asleep holding hands and smiling blissfully, the adorable redhead sandwiched in the middle until the sun rose and roused them from slumber.

But even though she was enthralled in the midst of domestic bliss, Ruby remembered to help her friend.

The Day After the Sleepover – Evening – Hakodate

After a long day of attending to their family run restaurant, Seira wandered into her bedroom, more than ready to let the day's stresses melt away into her sheets. But as soon as she stepped through the door, she found those plans going up in smoke as she beheld her adorable little sister, sitting bashfully on her bed wearing nothing but a blush and a two piece set of matching dark violet lingerie.

"Ria? What are you doing? And why aren't you wearing your pajamas?"

"Onee-sama," began Ria as she stood, "I... I need to tell you something. Something important."

Seira closed the door behind her as she approached the meeker girl. "Of course. What's troubling you, Ria?"

"Onee-sama, I've always... I've always admired you. Ever since we were little. Even before A-RISE, and Muse, and all the school idol groups that have come since, you're my first idol and you always will be."

"That's kind of you to say. Thank you."

"It's just the truth..." she muttered, looking away. "But recently, whenever we're together or whenever I think about you, I feel... strange. My heart starts beating weirdly and I get red all over."

"Oh my. Are you alright? Do you have a fever?" Seira moved close to press her forehead against Ria's, but the little sister pulled away.

"Onee-sama, wait! It's not a fever!"

"Then... what is it?"

"I... I'm in love. With you, onee-sama."

Seira merely stood there, blinking.

"Um... that's what the underwear is for. I was told that- I mean! I thought it would... help convey my feelings. To you. So... I want to give you my everything, onee-sama."

Ria clenched her eyes shut and looked to her feet, trembling in fear and anticipation. Then she felt a pair of strong arms wrap around her in a gentle hug, and Seira leaned in to whisper into Ria's ear.

"Oh Ria... My dearest, most precious imouto... I love you too."

Ria's amethyst eyes snapped open in shock. "Really?!"

"Yes. Both as a sister, and as a lover."

"Onee-sama..." Tears of happiness began to fall from the little sister's eyes, and Ria smiled as she returned the hug, never wanting to let go of her precious older sister. She couldn't help but cry. "I'm so happy..." she sniffed.

Seira pulled back slightly on noticing Ria's tears and, still keeping one hand hugging her sister, used the other to gently wipe away the tears. "Shh..." she cooed, "It's okay. You don't have to cry." She leaned in towards her nearly naked sister, pressing their noses together, their lips mere millimeters apart. "Would you like me to kiss away the tears?"

"Yes..." breathed Ria.

And Seira kissed her. Softly and lovingly, their lips touched in the darkness of the Hakodate night, the first kiss of many more to come.

~END~

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Omake:

"So... aren't you going to ask about the underwear?" asked Ria.

"Of course not," replied Seira as she stripped out of her clothes. "I've seen enough hentai to know where this is going..."