My sister's mate became mine after they stole my core

Life carried on as it always did—cold, heavy with judgment, and full of whispered scorn from my family and the pack. But something had shifted, something I couldn’t ignore.

The entire pack had begun to treat Bianca like she was the Luna.

It was subtle at first—more smiles when she passed, more bows and lowered eyes—but now it had grown into something undeniable. They praised her. Followed her. Worshipped her like she was the true mate of the Alpha. Like she was me.

We had the same face, the same voice, but our cores were different. That was what mattered. My core was what connected me to Mark. My core was the reason we were fated. And though I’d lost it, I was still his mate… wasn’t I?

But that wasn’t the only change.

Mark had changed too.

He smiled more when Bianca was in the room. His entire energy seemed to brighten with her presence, as if she carried the sun in her hands. And when she wasn’t around? He was cold. Distant. Tired.

I tried to reason with myself, telling my heart that they’d known each other since childhood. That we all had. That his closeness to her was nothing more than comfort from an old friend. But I couldn’t unsee the way his eyes lingered on her… the softness in his gaze that I hadn’t felt in months.

He used to look at me like that.

But now, when his eyes found mine, they were dull. Empty. As if I had become a burden. As if loving me had become a chore.

I told myself it was the core—my missing wolf—that made things difficult for him. Still, hadn’t he promised to love me through it all? Hadn’t he said he'd never leave me? That I was everything to him?

One morning, I woke with a wave of nausea so strong it forced me out of bed. Mark wasn’t beside me—again. My stomach churned, but this time not from pain or fear. Something felt different.

Hope fluttered in my chest.

I’d been feeling off for weeks, and finally, I decided to confirm what my body had been trying to tell me. I retrieved the test kit I’d bought in secret and rushed into the bathroom.

The moment the two lines appeared, my heart soared. I was pregnant.

I stood frozen, hands trembling with joy. For the first time in months, I felt alive. This… this was hope. A new beginning. A reason to smile again.

Without wasting a second, I showered, dressed, and rushed through the hallways of the pack house to find Mark. He had to know. I wanted to see his face light up, to feel his arms wrap around me with joy. This child would bring us closer again—I was sure of it.

When I reached his office, the guards at the door stepped forward, blocking my path.

“I’m sorry, Luna,” one said with a slight bow. “The Alpha is in a meeting and cannot be disturbed.”

My heart sank. “Please… it’s urgent. He’ll want to know this.”

But they stood firm.

I was about to argue when something made me freeze.

A sound. Faint, but unmistakable.

A moan.

My eyes darted toward the door. The guards exchanged nervous glances, trying to avoid my gaze. Then the sound came again—clearer this time. And it wasn’t just any moan. It was familiar.

My stomach dropped.

“Open the door,” I said, my voice barely above a whisper.

The guards hesitated. One looked truly pained as he said, “Luna… please. Walk away. Pretend you didn’t hear anything. It’s better that way.”

But I couldn’t walk away. I wouldn’t.

“Open. The. Door,” I repeated, this time with steel in my voice.

He sighed, defeated, and pushed the door open.

What I saw inside shattered me.

Mark—my mate—was on top of my sister, their bodies tangled on the desk as their moans filled the room. I stood frozen at the threshold, unable to breathe, unable to think. My heart cracked in my chest as if it had taken a physical blow.

Then Bianca’s eyes met mine.

She didn’t flinch. She didn’t hide. Instead, she smiled.

My legs went numb.

“Mark!” I screamed, and he stopped abruptly, turning his head toward me.

For a second, I hoped he’d jump up, explain, say it wasn’t what it looked like—some pathetic excuse like all cheaters do.

But instead, he snapped, “Are you insane? Barging into my office like this?”

My eyes widened. “But I’m your wife! What are you doing with my sister?!”

He climbed off Bianca and zipped up his pants like nothing had happened. He stepped toward me and… laughed.

“Wife?” he scoffed. “You? You’re nothing. A wolfless, useless shell.”

His words hit me like knives. I staggered backward, gripping the doorframe for support. Tears spilled down my cheeks. “You… you know what they did to me. You know. Why are you saying this?”

He looked down at me with disgust. “Because I’m tired of pretending. You think I wanted this? You think I was happy the Moon Goddess cursed me with you as a mate? Every time I look at you, I see what I lost. What I could’ve had.”

My eyes flicked to Bianca, who was still lounging on the desk like nothing had happened.

“You don’t even look guilty,” I whispered.

She stood up, brushing imaginary dust from her clothes, and walked toward me with a smirk. “Why would I feel guilty?” she said sweetly. “I’m finally getting everything I deserve.”

“What… what are you talking about?” I choked out.

Mark crossed his arms as Bianca stepped closer, pulling down the neckline of her shirt to reveal her chest. My breath caught.

There were scars.

But they weren’t like mine—jagged and rough. Hers were precise. Clean. Surgical.

“I took your core,” she said, smiling like it was a badge of honor. “And now… your mate belongs to me.”

My vision blurred as the world tilted around me. I couldn’t breathe. I couldn’t think.

“You… you planned this?” I managed to say through sobs.

Bianca’s voice was dripping with mock sympathy. “We didn’t want to. But when the Moon Goddess paired him with you, we had no choice. Mark and I have loved each other for years. We were just waiting for fate to catch up. When it didn’t, we made our own.”

I almost collapsed to my knees, sobbing, my hand instinctively going to my stomach.

There, beneath the crushing weight of betrayal, was the only thing that gave me strength:

The baby.

Our child.

But even that joy was poisoned now.

Because the man I had loved… the man I had trusted… had never been mine at all.