Honkai Star: Rail x Reader Oneshots

To Live is to Pretend | Sunday x Mimic Monster!Reader

Summary: During the Charmony Festival, Sunday encounters a mysterious individual—you—who is a mimic-based monster pretending to be human. Despite your awkwardness and strange behavior, Sunday sees through your facade and becomes intrigued by your desire to understand humanity. As the two of you spend time together, Sunday acknowledges your efforts and the shared desire for joy, even in imperfection. Ultimately, he finds something human in you, despite your differences.

Tags: Sunday x Reader, Mimic Monster!Reader, Emotional Exploration, Humanity, Fluff.

The glow of the Charmony Festival filled the streets of Penacony with music and laughter, as delicate as the wings of the butterflies flitting through the air. Among the throngs of joyous attendees stood Sunday, his piercing eyes scanning the crowd. His presence exuded a calm authority, every step deliberate, his voice a melody when he spoke. He lived for this—a moment where humanity could forget its struggles, even for a while. But he wasn’t here to simply bask in the celebration. His mind never truly rested.

And you...you were part of his latest dilemma.

Sunday’s sharp eyes had seen many things in his life, yet he could hardly make sense of you. Your smile was too wide at times, your laughter half a second too delayed. The way you moved—a little too fluid, a little too precise—made even the most distracted observer notice something...off. And your hunger. That was a beast of its own. It wasn't human hunger. It was a gnawing, endless craving for sustenance that wasn’t food. Something primal. You hid it, but not well.

Yet you were kind, earnest, and oddly endearing in your awkwardness. Sunday couldn't decide whether you were utterly harmless or an enigma with secrets darker than you let on. He had invited you here today to learn the truth.

“Doesn’t it feel alive?” you asked, looking up at the floating lanterns dotting the evening sky. Your voice wavered slightly, as though calibrating itself to match the tones around you.

Sunday tilted his head. “Alive? How do you mean?”

“They’re like...tiny creatures, glowing, free. Like they’re whispering to the stars.” you explained, your fingers twitching nervously as though rehearsing what a human would do. It was clear you were trying to fit in, but every gesture felt off, as if an artist had painted you from memory rather than reality.

Sunday’s eyes lingered on your face, the halo behind him casting soft light. “You see the beauty of it all, even in ways others don’t.” There was no accusation in his tone, only curiosity. “You’re not quite like anyone else, are you?”

Your movements stilled entirely, an unnatural freeze in the midst of your nervous shifting. “W-What do you mean?” The way your voice crackled betrayed your panic.

“I mean exactly what I said,” Sunday replied, taking a step closer. He loomed, but his presence wasn’t threatening—it was grounding, as though even the world’s chaos would fall silent before him. “You’re different, but difference isn’t a crime. Though I wonder, what is it you truly want?”

Your shoulders slumped, the pretense you’d worked so hard to maintain unraveling before him. “I-I’m not trying to hurt anyone,” you said quickly, stumbling over the words. “I just...I wanted to see what it’s like. To live. To feel.”

Sunday’s expression softened, though his eyes remained sharp. “And this...you mean this festival? Or this world?”

You hesitated. “Both. Humans. I think you call it ‘being human.’ I...I thought I’d try it out.” You chuckled, the sound awkward and hollow. “I’m...not great at it, huh?”

“No,” Sunday said, though the word wasn’t cruel. “But that’s not a failing—it’s an effort. Tell me, do you find joy in pretending?”

The question was so gentle that it made your chest ache. “I don’t know if it’s pretending,” you admitted, your voice quieter now. “It’s...wanting. I want to understand. To belong. But it’s hard.”

Sunday studied you for a long moment, his gaze weighing far more than it should. Then he smiled. “Perhaps you’re closer to human than you think.”

Your head tilted instinctively, mimicry of curiosity despite the genuine confusion you felt. “What do you mean?”

“You desire, you strive, and you falter. You want joy but fear pain. It’s the same for them all,” Sunday said, gesturing to the crowds. “Perhaps the only difference is that you know you’re not one of them. Most don’t even see that much.”

As the festival carried on, Sunday remained by your side, the only one who seemed unfazed by your oddities. For the first time, you felt as though someone truly saw you. Not your disguise, not the gaps in your humanity—just you.

And for reasons you didn’t quite understand, you hoped he’d stay.