Chapter Text
The city was quiet. Too quiet.
Night air hung heavy over the rooftops as Leo crouched at the edge of a crumbling mystic portal rift, his hand resting on his katana. They had thought the Kraang were the end. The final boss. But even with the invasion behind them, mystic anomalies kept bubbling up across the city like the world hadn't quite stitched itself back together.
"Rift’s closing," Donnie announced behind him, typing into his wristpad. "That’s the third one this week."
"Yeah, and they’re getting nastier," Raph grunted as he hauled a collapsed stone pillar out of the alleyway. "Whatever's leaking through, it ain't friendly."
“Any signs of Kraang energy?” Mikey asked, spinning his nunchunks in his hand.
“Nope,” Donnie said, narrowing his eyes. “This isn’t Kraang tech. It’s older. Raw. Like someone carved the spell by hand.”
Leo turned, expression taut with worry. “So, some mystic punk playing with forbidden magic?”
“Basically,” Donnie confirmed. “And judging by the power output, they’re either reckless or stupid.”
That was when the air snapped.
A ripple of distortion shimmered across the alley like heat off pavement—except this shimmer had teeth. A cloaked figure burst from the shadows with a jagged staff glowing sickly green. Runes cracked and pulsed along its length as the figure chanted in a tongue that twisted on the tongue.
“Move!” Donnie shouted.
Leo surged forward, blades drawn, but he wasn’t fast enough.
The staff slammed into the ground with a blinding flash, and an arc of energy shot straight into Leo’s chest. His eyes widened, body convulsing with the force as the spell wrapped around him like glowing vines.
“LEO!” all three voices called out at once.
He hit the ground hard. Smoke rose from his plastron.
Raph cried out in rage as he ran towards the unknown figure
"Have fun trying to remember your loved one" the unknown figure snarled in a low voice before producing a smoke bomb and vanishing
The brothers were confused on what the figure meant but didn't have much time to think about as they ran towards their brother in blue
Donnie was the first to reach him, dropping to his knees, hands and wrist tech frantically scanning for vitals
“Leo, come on, talk to me—” Donnie called out desperately, images of seeing Leo splayed out on the ground on Staten Island flashing through his mind
Leo blinked, dazed. “...Ugh. That guy could really use a mint.”
Donnie exhaled shakily. “Okay. Sarcasm intact. That’s good.”
“Where… where’d he go?” Leo asked, struggling to sit up.
“Used a smoke bomb. Vanished into the portal rift,” Raph growled, cracking his knuckles. “Coward.”
“Should we take him home?” Mikey asked.
“Absolutely,” Donnie said. “I’m not detecting any structural damage to his system, but that magic wasn’t just flashy. It was invasive.”
Leo looked around slowly. “Everyone okay?”
“Yeah,” Donnie said gently. “You took the hit for us.” before mumbling underneath his breath "As you always do"
Leo smirked as if he didn't hear Donnie. “You’re welcome.”
.
.
.
Back at the lair, the atmosphere was oddly calm.
Leo leaned back on the couch with an ice pack on his head, grumbling about how rude the staff blast was. Mikey was whipping up some post-battle snacks, and Raph hovered nearby with a worry line creasing his forehead.
Donnie returned from his lab with a scan report. “No signs of lingering dark magic, but I’m going to keep monitoring—”
“Who are you?”
Donnie froze mid-step.
Leo was staring directly at him, head tilted, eyes blank.
“…What?”
Leo gestured lazily. “You. The purple one. You’re not April. Or Raph. Or Mikey.”
Donnie’s smile faltered for a second before breaking out into a laugh, thinking that Leo was just playing a joke on him. “Ha-ha. Real funny, Leo.”
Leo frowned, not understanding on what was so funny. “I’m serious. I don’t know you.”
The room went silent.
Donnie felt his heart stop, unable to process on what exactly was happening
Raph stood slowly. “Leo, don’t mess around.”
“I’m not,” Leo said, growing uncomfortable. “I… I know you guys. Mikey, Raph, even Dad. But he—” Leo pointed at Donnie— “I’ve never seen him before.”
Donnie didn’t speak.
Not when Mikey whispered his name.
Not when Raph stepped between them like he needed to. Like his big brother was trying to protect Leo from Donnie. Which was absoutely crazy as Raph never needed to protect the twins from each other. Pull each other away from arguments sure, but Leo would never hurt Donnie, and Donnie would never hurt Leo. They were twins. They loved each other too much to even think about hurting each other. At least emotionally
And now, Leo was looking at him like he was some stranger
Donnie didn’t move, didn’t breathe.
He felt like time had stop and he was frozen in place
Just stood there, staring at the twin he had known since the moment they cracked out of their eggs together. Since they were mutated together and became brothers. Twins. Not just by blood, but by love
And that twin didn’t know him.
Didn’t remember him.
Leo looked at Donnie like he was just meeting him for the first time
Like the past 16 years of their lives was just wiped away
Donnie’s voice, when it came, was hollow.
“…I see.”
He ignored the calls of his name from Raph and Mikey
He turned, slowly walking back toward his lab—because he had to figure out what was broken.
And how to fix it.
The door to his lab slid shut behind him with a hiss far too loud for the silence it broke.
Donnie stood in the center of the room, blinking as the soft purple lights of his monitors cast long shadows over half-finished projects. Code blinked across a hologram—one he’d been building to track mystic rift patterns. It felt laughably irrelevant now.
His legs moved before his mind caught up, carrying him toward the back corner—his “sanctuary within the sanctuary.” The one only Leo ever really came into uninvited.
The chair was still pushed back from the last time Leo had slouched into it, tossing popcorn at Donnie while begging for “just five minutes” of company. That chair. That corner. That laugh.
Gone.
He lowered himself onto the stool and clasped his hands together tightly.
He doesn’t remember me.
His mind repeated it, cold and mechanical, as if saying it enough would take the sting out. Like it was just another glitch to be debugged.
But no line of code could fix this.
Donnie exhaled sharply, drawing in a breath that stuttered and hitched halfway through. His jaw clenched. He tried to focus, to analyze. The spell—it was absoutely some memory spell. However the big question that Donnie didn't know the answer to was what did the spell target? Selective memory? Emotional tethering?
The only thing that Donnie knew about the spell was that it somehow only target Leo's memories of Donnie. Leo remembered Raph and Mikey, and even their dad. Somehow, it was only him that Leo forgot. Why him? Why was the universe so against him? Why did this spell make Leo only forget him?
Could the spell be unraveled with the right calibration of mystic energy and psychic reinforcement?
Could he build something to simulate the bond they’d lost?
Could he force Leo to remember?
Donnie buried his face in his hands.
No. No, you can’t force someone to love you. You can’t rebuild a bond that one half doesn’t feel anymore. You can't rebuild a lifetime of memories and secrets. You can't make someone remember 16 years of a twin bond...16 years of twin love.
The thought hit like a punch to the plastron.
Leo remembered everyone else. Everyone. All of the times that he laughed with Mikey. All the times that he fist-bumped Raph. Probably even remembers the time that he rolled his eyes at Splinter’s latest meditation lecture.
But when his gaze landed on Donnie, it was like looking at static.
No flicker of recognition. No twin sense. No warmth. No love
Like a piece of Donnie had been carved out and discarded, and no one noticed until now.
“I—I don’t know you,” Leo had said. Not cruelly. Not even harshly.
Just… honestly.
The worst part?
He meant it.
Donnie’s breath shook. His vision blurred, and he realized distantly that he was crying—actually crying—without noise, just tears slipping down into his palms as if his body knew how to mourn what his brain wouldn’t admit was gone.
The bond wasn’t just broken.
It had been erased.