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Ruby couldn't remember when she had fallen in love with her own sister. Night after night, she stole secret glances at Dia, not daring to wish for anything more. They were sisters, after all, and they couldn't be anything more than that. Her feelings were immoral, improper, but as long as she was careful, no one would ever be the wiser. But one night, Dia had caught one of her stolen glances, and everything had changed.
Late at night, Ruby tried to stifle a cry as Dia's lips find their way between her thighs. Their parents were away on a business trip, so they had the house to themselves, a rare moment alone together, but still Ruby feared being caught. In school they hardly spoke to each other, and during practice it took all of Ruby's willpower that to stare at her sister's powerful movements, and her heart ached. She wanted more, but if the rest of Aqours find out…
No. This time belonged only to her and Dia. No one else would ever know, and only Ruby would ever see this side of Dia. That she could share such a secret with her beloved sister - her body trembled in anticipation.
Dia's lips were warm against Ruby's sex, and as Dia inhaled deeply, Ruby squirmed and her feet scrambled to find friction on the carpet. Dia, beautiful Dia. Her sister was strong and perfect, and everyone loved her. No one worked harder than Dia, and she always did her best. It was only natural everyone would admire her, and sometimes Ruby wondered if they hadn't been born sisters, would Dia have ever looked in her direction? Or would Ruby have just been yet another faceless girl in the masses, too afraid to confess her feelings?
Ruby shut her eyes tightly, trying to blink away tears. Even if this love was wrong, even if good sisters wouldn't do something so shameful, she was thankful to have been born as Dia's sister.
"S-Sis…" Ruby moaned as she tangled her fingers in Dia's long, soft hair. Dia's fingers were tight around Ruby's thighs, nails digging in the flesh, and Dia's tongue prodded Ruby's entrance, teasing her with promised pleasure, and Ruby couldn't help but whimper.
Dia's tongue was moist and certain, caressing the folds of Ruby's sex, and she didn't hesitate as she pressed her face more against Ruby. Ruby's entire body began to tremble, and as she trailed her fingers along Dia's scalp, she could feel Dia's body shivering as well. Dia brushed her teeth against Ruby's clit, and Ruby nearly cried out, but familiar fear filled her, so she bit down hard on her lip to silence herself, nearly drawing blood.
But she didn't have anything to fear, she told herself. They were alone together right now. They had the whole house to themselves. This time was theirs alone, and only theirs, and she didn't want to waste a single moment.
Dia kissed Ruby's clit and gave it a gentle but firm suck, and Ruby could no longer hold back her moans. She spread her legs further apart as she pressed Dia's head more between her thighs, and Dia's lips became more eager. Her pace quickened, her lips and tongue fervent as they engulfed Ruby, and Ruby's body quivered with pleasure.
When Ruby came, she let out a loud cry, but Dia didn't stop just yet. She kept going, and the pleasure that filled Ruby was almost painful, and as that pleasure shuddered throughout her aching body, her mind went blank and her body hit the bed with a soft thump.
As Ruby calmed, Dia lay next to her and tucked a strand of hair behind her ear. "Was that too much?" Dia asked, her green eyes filled with worry.
A smile tugged at Ruby's tried lips; Dia was always so considerate. "No, it was great," she said as she rested her head on Dia's chest. "You're amazing, Sis."
Dia sighed into Ruby's hair as her arms came around Ruby's back. "Are you really okay with all this?" she whispered, her voice quivering. "We don't have to-"
"Yes, I want this," Ruby said quickly, too quickly. "Because I love you."
Dia simply smiled, a faint, careful smile, and she brushed her lips against Ruby's forehead. Ruby put her arms around Dia's back to hold her tight, and the sound of Dia's racing heartbeat filled her ears.