The kiss was not a grand, cinematic moment. It was a soft, hesitant, and world-shatteringly terrifying collision that lasted for maybe three seconds. When Rina pulled back, her face was flushed a brilliant, triumphant red, and my own face felt like it had been set on fire. The air in her room was thick with the fallout, a mixture of her giddy audacity and my pure, system-crashing panic.
"So," she said, her voice a breathless, victorious whisper. "That happened."
I could not form words. My brain was a blue screen of death. I just stared at her, my lips still tingling with the ghost of her touch, which felt both impossibly soft and dangerously radioactive.
This could not happen. This was the one line, the one sacred, absolute rule of our universe, and we had just stomped all over it. I needed to be the adult. I needed to be the responsible one. I needed to re-establish the boundaries before our entire lives spiraled into a black hole of romantic-comedy-turned-tragedy.
I took a deep, shuddering breath. "Rina," I said, my voice coming out as a strained croak. "That… that can never happen again."
She just smiled, a slow, infuriatingly smug smile that told me she was not taking this seriously at all. "What? The kissing? Or the winning?"
"The kissing!" I hissed, my voice a panicked whisper. "This is wrong! We are brother and sister! This is the fast track to a lifetime of therapy and awkward family dinners!"
"I don't know," she said, tilting her head and tapping a finger on her chin, pretending to consider it. "I thought it was pretty nice. A solid seven out of ten. Maybe an eight if you were not so tense."
"This is not a joke!" I insisted, running a hand through my hair in pure desperation. "We have to have boundaries. Strict boundaries. This- the teasing, the jokes, the… this," I gestured vaguely at the space where the kiss happened, "it all has to stop. We have to go back to being normal."
She looked at me, her eyes sparkling with a mischievous light. She stepped closer, stood on her tiptoes, and patted my head like I was a nervous puppy. "Okay, Onii-chan," she said, her voice full of a cloying, condescending sweetness. "I promise. No more unplanned, spontaneous, emotionally charged kisses. I will be on my best behavior."
Her promise was worth less than the air she spoke it on. I knew this with a terrifying certainty. I had not established a boundary. I had just handed her a new challenge.
The next morning was a testament to my failure. I stumbled into the kitchen, having barely slept, to find her humming cheerfully as she made breakfast.
"Good morning, my beloved, but strictly platonic, brother!" she chirped, sliding a plate of perfectly cooked pancakes onto the table. "I was just thinking about our future. We will have to be very careful not to accidentally fall in love, get married, and have three beautiful, artistically talented children. That would be a real social faux pas."
I choked on my coffee, a hot, bitter spray erupting from my mouth. She just patted my back, her touch lingering a moment too long. "There, there, Onii-chan. Do not get so worked up. It is just a hypothetical, completely forbidden future."
She spent the rest of breakfast detailing this hypothetical future, including the names of our hypothetical children (Starlight and Knight, of course) and the breed of our hypothetical dog (a Shiba Inu). I just sat there, a silent, horrified captive at my own kitchen table. The battle was over. I had lost. My life was now a romantic comedy, and my sister was writing the script.