Summary: Todoroki Shimoka wasn't in anyone's plan but no matter. She, with her weaker quirk, would be Shouto's sidekick—or at least, that's how it should have gone. No one expected the girl to have past memories, much less be a former mafia boss. And Tsuna... Tsuna just wants to his family back.

Prologue

(When a sky loses its elements...)

His intuition roared loudly in his head and in instinct, his body moved. He pushed his unaware Lightning Guardian from the incoming attack, taking a direct hit in his stomach. Blood fell on the ground and his amber with hinted golden eyes narrowed at the unfamiliar attacker.

"Lambo," Tsuna whispered grimly, not taking his eyes off the strange man and he took a protective form between his claimed younger brother and the enemy. "Go and call Reborn or Kyoya. It's a Code Red."

Wide and fearful eyes snapped at him but he didn't pay attention. He refused to let the younger man join the fight. This stranger was too much for Lambo...or even him at his current state.

"But Tsu-nii—"

"Go, Lambo! Leave now!"

Lambo tried to protest again when the stranger suddenly disappeared and reappeared in front of the black-haired man. Tsuna gritted his teeth and once again intercepted the attack.

Orange hues fading into golden orbs, the mafia boss maximized his flames into his left hand and punched the stranger at his most powerful. He wanted to continue trying to get his guardian out but he underestimated his body condition and his wound deepened.

He dropped on the ground with Lambo following and checking on him frantically.

"Tsu-nii!"

He had lost too much blood. They had been fighting for hours by now and the attackers did not seem to be decreasing in numbers. This battle had gone too far.

"Tsu-nii, I'm going to carry you."

A hand scooped him and moved his bleeding body from the ground. His carrier checked on his pulse and seemed to be frozen for a second before the young man dashed away.

"I need to find Ryohei-nii!"

Why was everything running in circles? Everything seemed to be blurry.

"Find Ryohei-nii or Baka-Reborn. Just anyone!"

Was that Lambo? His vision was blurry at best and his other senses were fading away faster than he expected. He definitely was losing far too much blood.

"Baka-Reborn! It's Tsu-nii! He's—!"

Tsuna should probably assure Lambo that he would be okay. His injuries would heal and that the youngest guardian shouldn't be crying. The other man was already twenty, after all.

But he was tired.

'A little nap can't be help, can it?'

His amber eyes closed as all his senses faded into abyss.

Then, there was a snap and he lost all his connections to his elements. And the overwhelming pain followed.

An unfamiliar heat enveloped his whole being and burned all the trends of connection he tried to grasp, while a chilling cold drowned him into nothingness and froze his entire soul. As if cleansing and emptying his body with nothing memories to remain.

'No, no, no!' He denied the heat and coldness of his body and tried desperately to grab onto his connections. They were slipping away and there was nothing he could do.

Tsuna cried out loudly and despairingly, utterly crushed beyond repair.

And his Sky Flames raged.

Skies were naturally accepting and forgiving souls that normally wouldn't rage, but no Sky would let anyone take their elements. No one. Not even Death itself.

Sawada Tsunayoshi died protecting everyone he cared for and lost everyone in the process. So, his rage followed even in his next life, changing everything and nothing in the process.

Years passed.

Tsuna, as blank and emotionless eyes clashed into his, wondered if it was his fault.

"W-wait!"

His shaking and high-pitched voice echoed in the room that was once theirs. His heart beat quickened its pace and the core of his soul flickered. He looked at this person, who he had greatly failed, pleading with eyes of the same color.

Something flashed in those previously blank orbs and a familiar heat hesitantly flared.

Tsuna tried. He really did. With all his might, he tried to not make the same mistake. He forced his body to stay still. His breathing suddenly stilled and all his thoughts froze. He really tried his best.

But—

A figure of a lone yet reliable man smirked slightly, his eyes softening as he leaned forward.

"Little Animal," he called that familiar nickname, anticipation clear as his intent "Fight me. I'm bored."

—no!

Almost instinctive, almost reflexive, almost immediate, an invisible wall dropped and stopped the other from reaching him. His eyes automatically closed and his body flinched.

It was just an instant, but an instant was all what's needed.

Tsuna realized what happened and he quickly opened his eyes. However, it was too late. He—no, she—felt her heart breaking and it's all her fault again.

Todoroki Shouto, her beloved twin, stood there with such disappointed and crushed spirit, and it was all her fault.

'I'm sorry. This is all my fault I'm sorry,' those words got eaten by her guilt and she could only stare at the boy with tears. Knowing exactly what went wrong but not wanting to do anything about it.

'I can't be it, Shouto-nii.'

The boy, who grew up together with her for the five years of her second life, withdrew all his emotions and walked away.

Todoroki Shimoka said nothing in return.

Once upon a time, their lives were easier. With more laughter and smiles. Once upon a time, there was happiness. However, once upon a time never last and only regret and sadness remained.

'I'm sorry. I just can't be your sky.'

Because Sawada Tsunayoshi died with many regrets and blood in his hands while Todoroki Shimoka lived with all the memories and mistakes.

Because Tsuna had his elements and lost them while Shimoka remembered and never wanted to replace anyone.

Because Hibari Kyoya was Tsuna's Cloud while Todoroki Shouto was Shimoka's twin brother.

~0~

When Todoroki Rei was pregnant with twins and felt like dying from the heat and chill in her stomach, Todoroki Eiji knew that this pair would be his ultimate weapon against All Might. Rei just hoped for the best for her two unborn children.

When the twins were born, Shouto gave out powerful and loud cries while Shimoka never once cried out and merely stared at everything blankly. Eiji decided that the former was stronger and the latter could be a sidekick. Rei worried a lot about her husband's plan but what worried her the most was the emptiness in her youngest daughter that mirrored her own.

When the two kids got their quirks at the same time, Shouto had an overwhelming ice and fire power while Shimoka had support-like power. Eiji knew that his first decision was correct and that these two would be the best. Rei felt her heart breaking every time she had to watch her so-called husband trained her youngest children to the bone, eyes tearing up when she saw the bruises on her son and the fake smiles of her daughter. And she could do nothing to help.

When Rei snapped and Eiji forced himself to send her away, his vision seemed to waver and he finally noticed all the alarming signs on his children. Natsuo glared at him with hatred. Fuyumi flinched at him with fear. Shouto stared at him with disgust. Shimoka smiled at him with blankness. And Toya...Toya was dead.

Oh God, what had he done?

(...the whole world got turned upside down.)

A/N: Can you guys believe how this story is actually from the idea where I wanted Tsuna reincarnated as Shouto's younger sibling and made Shouto overprotective of him? Yeah, that classic humor is the only reason why I created this, but because of Endeavor's goddamn Parenting/Husband skills, it turned into this angst. Basically, KHR died in their universe horribly and all their regrets and memories got carried on their life in MHA. And it totally messed up the canon in a subtle way.

Also, Tsuna's new name is Todoroki Shimoka. It was hard trying to find a name that meant fire and ice (because of course, Endeavor would name his children like this) but I found that Shimoka means "frost fire". It's close, I guess?

Subtle Change #1: Ah, look, remorse Endeavor! But no worries, this Todoroki Family business is still in a deep shit.
Subtle Change #2: There are Flames here and they are different from quirks.
Subtle Change #3: Shouto is an inactive Cloud that wants to harmonize with Shimoka/Tsuna's active Sky Flames.