Longer summary:

After the turtles recover an ancient weapon meant for the Shredder, a Leonardo from the future visits the turtles to ensure they get rid of this artifact— the Heiwa no Buki, or a tragic event will forever shatter the Hamoto family in days to come. With his help, the turtles must rewrite their destiny before the unthinkable happens to a member of their family. But with tension rising between Leo and Mikey, things are getting a little complicated. And when Mikey suspects his big bro from the future is holding something back from them, from HIM, his trust in his family is fleeting.

Can Mikey hold his faith in his brothers amid the most challenging time in his life?

Will this Leo from the future successfully save his family from a fate most terrible, or will history repeat itself?

Hi! I've never written in this fandom before, but I've been a fan of TMNT for years. This is basically in the 2012 universe, but no specific time. I apologize if the chapters start out pretty short. I plan on them getting longer as the story progresses. Please review if you see any issues as I'm trying to perfect my writing. Writing something like this is an awesome practice to get me out of my writer's block.

I hope you enjoy!

2027

Miserable silence hung in the lair, just as it had for the past five years. It staled like the gut-wrenching malodorous sewer smell they've grown accustomed to.

It felt like years since someone released a hearty laugh down here under the streets of New York City. Not like a slight chuckle or sneer, but an actual laugh from the gut, a symbol of genuine amusement. The mood of their once happy home only shifted when April and Casey came to visit, but unfortunately for Leonardo and his brothers, that only transpired on holidays and summers. Their only human friends left for college a couple years ago. Well, April enrolled in college. Casey tagged along to be close to her. He almost didn't because of the event five years ago, the unspeakable tragedy that forever shook the Hamato family. The athlete was at first determined to stick close with his turtle brothers for comfort, but Raphael talked him into moving with April.

Even April had her worries about taking her life elsewhere, away from her mutant family, but Donatello shut her down immediately, encouraging her to indulge in her academics, imploring her that they would be fine. Leo wondered if it was really about April having her college adventures more than Donnie wanting to know every detail, wishing he could also attend. The blue-clad turtle grinned at himself.

He lay in his bed with a vacant stare glued to the pipes above, one of his katanas resting on his stomach. Gliding a thumb across the leather handle, he simmered in these thoughts as he did every night. He and his brothers should be out there, restoring honor to their shattered family, but the sun was out, and people were out. The Shredder and his brainwashed clan of disciples did the majority of their heinous work at night anyway. Still, even after five years, it felt weird to just lay around and do nothing when…when…

Leo shook his head in a desperate attempt to evade the burning sensation in his eyes. He was surprised he had tears remaining after training himself to let it go, pummeling the emotions out of him when his brothers needed his guidance the most. Of course, when he was alone, the emotions pummeled him.

"Ha…EUREKA! I did it! I did it!"

Donnie's voice emanating from his lab stirred Leo out of his deep thoughts, sitting up and sheathing his blade. He curiously exited his room, seeing his immediate younger brother, Raph, also stepping out to assess the commotion.

"You don't think he…." Raph's voice faltered, his chest hitching from an unexpected, excited breath.

The lab door flew open, and Donnie looked to his brothers across the way. "You guys, it's finished! I've actually done it!"

Leo and Raph exchanged grins for the first time in a long while, racing to the lab. The space used to be tidy and well kept, but since the event, Donnie had forced all of his attention on this project—second to getting revenge—and no longer cared for the state of his workspace. Leo couldn't help but take in the sight of numerous coffee cups in different areas of the lab, some caked in dust, and some with the bitter beverage left unfinished.

Behind the two turtles was master Spinter, hobbling in and taking a seat in a nearby chair after swiping over a stack of papers with his tail. These past years have taken a toll on their sensei, and along with his grief, Leo has buried that knowledge six feet under.

"This better not be a joke, brainiac," Raph threatened.

The purple-clad turtle shot a warning look at his brother, his weary eyes piercing even through Leo, who didn't dare make the comment. "I wouldn't joke about this, Raph."

Donnie stepped away, and Leo could finally behold it for himself. A real time machine. He couldn't believe it. "Don…this is incredible. You're sure it works?"

"It'll unquestionably work. But I have some unfortunate news," Donnie said. Leo, Raph, and their sensei each slackened their shoulders, prepared for anything. "Remember that power cell we stole from the Kraang just last year? Well…" Donnie exhaled, ready to ramble facts his family probably wouldn't understand, but held his tongue. "There's not enough energy for the three of us to go back in time. Only one can pass through before it shuts down."

"So…we have to pick who goes?" Raph asked, disappointment dripping from his New York accent.

"Precisely," Donnie sighed.

Leo stiffened, turning to his family. "I'm going. There will be no debating."

"What if I wanted to go, huh, fearless?" Raph demanded, poking a finger at Leo's plastron.

Leonardo's mouth tightened into a thin line. He stood tall against his brother in red, bumping against his chest enough to knock him back a step. "I said no debating, Raphael. What happened was my fault…I…I have to do this."

Raph's tight, irate eyes softened only slightly when he saw tears lining his older brother's. Out of all of them, Leo had been the strongest. To see him fighting back tears let him know just how much this meant to him. After a silent conversation through their stares, he begrudgingly nodded at Leo.

"I know you will do what's right, my son," Splinter said, clasping a fragile hand on his eldest child's shoulder. "Now go, rewrite the Hamoto history."

Leo pulled his father into a tight hug in place of his usual "Hai Sensei" with a respectful, stiff bow. No one had to be reminded of what changing their future entailed. They would cease to exist in this time, replaced with different versions of themselves. But it was worth it after the heartache they've carried for so long. All around him, Leo felt strong arms clinging to him and Splinter, ensnared in a group hug.

The warmth of his brothers and Sensei enveloping him forced the tears to fall as if they had squeezed them out of him, but he wasn't the only one letting go. Even Raph was shedding tears, sniffling into Splinter's greying fur.

"I can't believe this is finally happening," Donnie said into Leo's shoulder.

Leo nuzzled his head in Splinter's fur, remembering doing so as a child. "I love you guys."

"Yeah, yeah." Raphael cleared his throat and released them. "Go do your thing, bro."

Leo tried to conceal his uneasy gaze toward the machine. "Time traveling was never really my thing to begin with, Raph."

"You know what I mean," Raph grunted.

Donatello started punching in numbers on a screen to the machine's right, his shell hunched over. "Okay, I'm setting the date to midnight, January twenty-seventh, two thousand twenty-two. You'll know exactly where to find him."

"Thanks, Don." Leo nodded firmly.

The four squinted their eyes as the machine hummed alive, flickering white streaks in every available space. Leo soon realized that the humming wasn't the machine but the power cell trapped in a glass canister.

"It's already over-heating. Here's your window, bro," Donnie warned.

Leonardo allowed a small smile to grace his face. "I'll see you guys in the past."

In a blinding flash of white, the blue-banded turtle vanished.