Prologue

It was a Sunday in late September, autumn’s chill just beginning to settle into the air—

“Ahahaha! Aniki, you’re so pathetic!”

“Hey, wait! I told you to stop with those aerial combos! That’s completely unfair!”

—though the season had little bearing on how my stepsister Akira and I spent our time, lounging around the house and gaming as usual.

“Perfect! Not a scratch on me. Round one goes to me~”

“Damn it! I’ll turn this around in round two! This time for sure—”

…Actually, let me correct that. It would be more accurate to say Akira was toying with me.

The game currently humiliating me is End of the Samurai 2—or “Ensamu 2” as fans call it—a fighting game set during Japan’s tumultuous Bakumatsu period. Two years post-release, it’s become essential for any Bakumatsu history enthusiast. Unfortunately for me—

“Flawless victory!”

“Hng!? Not even a single hit of damage… I’m sorry I failed you, Yoshinobu…”

—being a history buff doesn’t automatically make you good at fighting games.

Thanks to my abysmal skills, the fifteenth Tokugawa shogun lies defeated once again, face-first in the digital dirt. As the victory screen loads, the cross-dressing swordswoman Nakazawa Koto adjusts her kimono with practiced elegance, a glimpse of pale collarbone visible beneath the loosened fabric.

“I won’t marry anyone weaker than me,” she declares with her signature arrogant smirk. “If you want me, prove yourself by defeating me first.”

Her standard victory taunt feels particularly cruel right now.

“Another win streak for me!” Akira chirps.

“And another losing streak for me… Seriously, Akira, don’t you think it’s time we moved on to a different game?”

I know this one holds sentimental value—it was the first game we played together after all—but at this point, it’s becoming my personal psychological torture device. Akira’s improvement over the past two months has been nothing short of terrifying. Someone like me, who only plays casually, can’t even land a single hit anymore. Just now, my Yoshinobu got demolished without dealing any damage whatsoever.

At this rate, I’m defeated mentally before each match even begins.

“Aniki, why don’t you try switching off Yoshinobu?” Akira suggests with the casual air of a seasoned pro. “Against Koto-kyun, that matchup is like seven-three in her favor. You’re fighting an uphill battle from the start.”

“Matchup ratios? And did you just call Nakazawa Koto ‘Koto-kyun’?”

“That’s what everyone calls her in the online forums. She’s strong, cool, and adorable, right?”

“…Whatever.” I wave her off dismissively. “Break time. Playing for an hour straight like this is brutal…”

Maybe it’s the accumulated frustration from my losing streak, but irritation creeps into my voice, as I drop the controller onto the coffee table and start to stand. Before I can fully rise, Akira’s fingers catch the hem of my shirt.

“Aniki…” Her voice drops to an uncertain whisper. “Are you maybe… getting tired of playing games with me?”

“Ah, no! That’s not it at all. I’m just feeling a little worn out, that’s all…”

Pulling that heartbroken expression out of nowhere should be illegal. If she were my actual brother, I could have laughed it off with a casual “No way” and a friendly shoulder pat. But she’s my stepsister—a girl—and that makes everything infinitely more complicated.

I find myself looking away awkwardly, feeling pathetic as an older brother.

“Actually, Akira, don’t you get bored playing against someone as weak as me?”

“Nope, not at all.”

“Why not?”

“Sure, Aniki’s weak, but I still want to play with you anyway.”

“…But why?”

I was about to point out that facing stronger opponents would be more exciting, but—

“Because Aniki’s frustrated expressions are just so adorable…” Her eyes grow soft and distant. “They make my chest feel all tight inside.”

“—What!?”

She said it with such genuine longing that my brain short-circuited.

“So please keep losing to me forever, okay, Aniki?”

…Honestly, hard pass on that request.

Akira’s goal isn’t simply to win—it’s to watch me struggle and fail, savoring every moment of my defeat. Even knowing this, I still desperately want to beat her, impossible as that seems.

“Ah, but I do want you to practice tons and get super strong! Strong enough to finally beat me!”

Did she just read my mind?

“R-Right? If I’m no challenge at all, it must be bor—”

“I won’t accept anyone weaker than me.” Her voice drops to a sultry whisper, perfectly mimicking Koto’s victory line. “If you want me… then show me by winning.”

“—ing…”

“Just kidding!” She breaks character with a giggle.

Has she been playing Ensamu 2 so much that Nakazawa Koto possessed her?

“Well, my heart already belongs to you, Aniki. But if you want to beat me in this game, that means you want me, right—”

“Which means maybe it’s better if you keep losing~”

“What!? Aniki, that’s so mean! You’re supposed to say ‘Then I’ll try even harder’!”

Akira begins playfully swatting at my shoulder, her mock indignation adorable despite myself.

Yeah, I really am a terrible big brother.

Not only did I initially mistake her for a stepbrother, treating her casually without realizing she was my stepsister, but ten days ago,  we ended up sharing the same futon. And then—

“So let’s get married, okay? Become a real family with me? I’ll treasure you and our future children forever, Aniki.”

She didn’t just confess her feelings. She straight-up proposed marriage.

When faced with Akira’s proposal, I told her, “I want to stay as your Aniki.” The truth is, I still haven’t sorted through my tangled emotions. Whether I see her as family or as a member of the opposite sex, my desire to cherish and protect her remains unchanged.

Akira, probably anticipating my hesitation, had cleverly prepared an escape route for both of us.

“So for now, I’ll remain your stepsister, but eventually… make me your bride.”

Eventually—with no set deadline attached.

Will Akira keep waiting for me until that undefined “eventually” arrives? Will I continue making her wait? Until the day I can face her feelings—and my own—with complete honesty…

Our relationship has evolved to the point where we’re balanced precariously on the edge of crossing that invisible line between siblings. But the paths we’re each envisioning haven’t converged yet. And for now, we’re tracing parallel routes, fragile and uncertain as they are.