Regret

Assumption

small note, there's a number of assumptions you'll make in this story, some will be answered later, and some may remain unanswered. 

"I don't accept someone like you to be Vongola Tenth," Gokudera hissed.

But I'm not Ienari, he wanted to say, but wisely, he kept silent. He wasn't sure if he did it out of a sudden jealousy or for the sake of not causing more trouble than a flipped desk.

  "Dame-Tsuna's already gotten on his bad side!" a boy laughed. In that instant, Gokudera turned back to him, scanning him. An overwhelming sense of familiarity nagged at him as he struggled to refrain from talking.

  Then, he looked around, finding and locking eyes with Ienari. He flipped his desk too.

  "Even Ienari?!"
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  "Sawada-kun, are you sure you can handle it?"

  "Yes, I—"

  "Give us at least half, I'm surprised you can even move your shoulder freely already."

  The Kurokawa of this world was scarier than the one in his, he sulked. Reluctantly, he allowed her to take some of the boxes, Kyoko taking some herself. A light flush colored his cheeks, and meekly said, "Thank you."

  "You've changed, Sawada," Kurokawa murmured lightly.

  "You've become kinda cooler," Kyoko remarked, a soft giggle that made his heart skip a beat.

  "He's still a monkey, Kyoko," she deadpanned.  "But he's got a different aura about him."

  Was he—his parallel self—more interactive with the two of them? The normalcy of it felt somewhat natural to him. He felt himself fade out of the conversation as the two girls discussed class matters he could vaguely remember from his own middle school years.

  He could tell immediate differences between himself and his parallel self. His parallel self was much skinnier, already frail with the arcobaleno curse only adding further damage. His academics were much higher than what he'd ever expect, and he was only called a dame when Ienari wasn't around.

  "Ienari-kun was pretty shaken up for the past two weeks, I heard from Onii-chan that the volleyball club had suffered greatly."

  Wait, what?

  "It's their fault for shoving responsibility as best player on him. He was struggling with family issues, and you expect him to still play at his best?"

  "He... seems fine?" he said dumbly.

  "Because you're alive and recovered, stupid," Kurokawa remarked.
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  "Yamamoto's about to jump off the roof!"

His breath hitched and he was about to speak, to convince that stupid rain to not kill himself over an injury and off-day when—

"He is Ienari's guardian."

"That doesn't matter, Yama—"

"Shut up and watch, dame-Tsuna."

Ienari started talking nonsense, the same nonsense he'd sputtered out the first time around, and the two of them fell off the roof just the same.

Reborn had shot a Dying Will Bullet in the last second, the two of them landing safely and void of injury. Half the student population freaked, both at what had just happened and the fact the two of them miraculously came unscathed from that fall.

Hibari's appearance had everyone quickly scattering down the stairs, knowing that crowding on the roof was the worst idea of existence when he was around.

"Your father had planned for the two of you to fight for the position, but given your position, it falls out of the question. You have to stay out of this, Tsunayoshi."

Warily, Tsuna kept his mouth shut, aware of the truth in Reborn's words. He bit back the urge to complain to his tutor, lowering his gaze in defeat. Calm down, Tsuna, there's no reason to be upset, he reasoned lightly. Wisely, he followed a good number of students down the stairs as they scurried to see what had become of the two fools to fall from the roof.

Yamamoto was smiling brightly, as though it hadn't happened, and Ienari only seemed baffled at how in the world could this guy be laughing at the fact he really just almost died, but Tsuna swallowed a smile.

"Thanks for saving my life that day, Tsuna."

"Thanks Nari."

"Y-you're welcome...?" Ienari spluttered dumbly.
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  He was the Decimo's catalyst, nothing more, nothing less, the realization came idly.
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  Jealousy? That wasn't the right word. Out of place, he concluded.

  He fiddled with the pacifier in his hands, wrapped in tiny chains that seemed so befitting of its user, a prisoner, an entity that didn't belong here. It was late evening, he could hear the boisterous trio being disturbed by Lambo and I-Pin in the room next door, feeling rather odd at not being present.

  Sawada Ienari was a practical parallel to him, from his looks to personality. Perhaps a better version of him, Tsuna once thought. He was charismatic, a natural characteristic of any sky,  he was affirmative and a fair judge. Hell, he was actually respected by his peers unlike him.

  He wasn't jealous of him in any of those aspects, it was more so he didn't realize just how much he relied on his friends. It was odd, watching each and every one of them converse with Ienari instead of him.

  "You have something to tell me, don't you?" he said softly, sitting up from his bed, and habitually stuffing the pacifier beneath his shirt.

  "You're not bad," Reborn remarked. He hopped onto the desk, eyeing the boy carefully.

  "Your father is coming home."

  "What of it?" he asked warily.

  "He has no knowledge of your current state, much less your position," Reborn said curtly. "I can assume you don't plan to stay much longer, either."

  "Twins are to fight to death for succession," Tsuna recited, heaving a deep breath. "I cannot say how long I'll be here."

  "Ienari knows you know, care to guess how?"

  It was his turn to double take. "Since when? Why hasn't he—"

  A smirk. "You're so gullible, Baka-Tsuna. The Vongola rings are coming with him."

  "He hasn't met—" quickly, he cut himself. "his Mist... guardian.... yet."

  He tipped his fedora, frowning. "He's already met Rokudo Mukuro, have you forgotten?"

  He cursed to himself, pulling his head down. The light in his room flickered idly, and he threw himself onto his bed, exasperated.

  "You were kidnapped in his place and nearly died," Reborn stated, staring at him. "Were you that traumatized that you forgot that easily?"

  "Of course not!" he screeched. "He got his Vongola gloves and Mukuro was taken by the Vindice and I was almost discovered! I'm not going to forget that quickly! It was just two days ago!"
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  "Tsuna, what's that on your neck?"

  Well, he was going to have a hard time getting out of that.