The existence of masks is such a strange thing.
In this world, everyone has a mask, a second face that tells you as well as everyone else what Role you'll be playing - that's how it has been since a long time ago. No one knows for sure where it came from or why it existed in the first place, only the fact that by the time you're a teenager, you would have already found your mask and would know what your Role is at that point.
That's why, the fact that Tsuna had yet to find his mask despite him already turning 13 came as a shock for Reborn. To not know what your Role is when everyone else does is both worrying and horrifying. Even Reborn, cursed as he was, still has his Master mask tied securely around his arm.
The average age for a person to find his mask is 8-12 years old. While there have been some cases where people find their mask at a much older age, the probability of it ever happening to someone is lower than 10%.
"I guess I'm too stupid to even have a mask," Tsuna had shrugged when he caught Reborn staring at him. "Maybe my mask is a one-of-a-kind kind of mask. A Dame mask. Maybe that's why I haven't found it yet, because it's taking too long for the gods to make it," the teen laughed emptily, causing even the great Reborn to feel uncomfortable at the unexpected dark humor from his charge.
(Reborn had then promised himself to kick a certain Lion's butt for leaving his own pride, his own family for Nono's Famiglia.)
While it did give him several (a lot of) challenges, Reborn did not have a Master mask for nothing. Just as he had mastered the arts of assassination and became the greatest hitman the world has ever seen, he will master the art of teaching and he will succeed in grooming the heir of Vongola to become someone worthy of being the leader of Vongola, with or without a mask.
"Stop acting like a useless human being, Tsuna. With or without a mask, I'll make sure you become suitable enough for the throne of Vongola." he had declared to Tsuna when he was helping him with his math homework. "Now stop whining and look at what I'm doing again. You're getting this part wrong, Dame-Tsuna."
He admits, it was an exhausting uphill climb to the top. With Tsuna's low self-confidence as well as his inability to find his own spine, it had taken Reborn a lot of patience and encouragement (that may or may not have guns involved in it) before he was finally able to see a glimpse of what a great man Tsuna could be in the future.
The Mukuro incident had been an unplanned risk that had paid off when Tsuna started to show the uncanny Vongola Intuition he inherited from his ancestor. The battle between the Varia was earlier than he had predicted but again, it paid off when Tsuna began to be more confident. The future-that's-not-theirs incident had been something even he could not have predicted but thankfully, everything went well without too much casualty (the fact that Tsuna experienced his first war and his first death was something that had weighed down heavily at the back of his mind) from his side. The conflict with the Shimon Famiglia as well as the battle against Daemon was an unwelcomed addition in his plan but Reborn made do with what he got.
It was during the Arcobaleno trial, the fight for the right to keep living (and how he hated the fact that his two students were risking their lives for his) that Reborn was given the chance to see an extraordinary sight.
Sawada Tsunayoshi, a boy who had been called useless since he could remember, a boy who was the only one to never have a mask, the boy who even though was a coward, was bravely showing everyone his maskless self, stood against Kawahira, a being older and stronger than him, and said, "No." with a decisive tone, wearing a mask on his face like as if it had been there all this time.
Later, much much later, when everything had calmed down and everyone had healed enough to not risk opening another wound, Tsuna showed to all of them the mask that he had finally found, and what he showed them caused everyone to widen their eyes in shock.
Tsuna's mask, his own mask, is one of the very old ones, the kind that's rarely, if ever, seen today anymore -a King. Reborn remembers learning about that kind of masks a long time ago. Everyone has. Old, strong, the kind that will wear you instead of the other way around if you're not careful, they have so much history - been in so many stories and beliefs- behind them.
And suddenly, Reborn can't help but want to laugh. A King of all things, he thought in amusement.
Those who possess the King mask can make anyone and everyone to obey them if they want to. Even a Rebel or a Rogue with no loyalty to anyone will follow the King's command if the wearer has a strong soul. And Tsuna is one of the strongest -if not the strongest Sky Reborn has ever met. For Tsuna to have that mask of all things? Fate really does have a twisted sense of humor. No wonder Reborn couldn't refuse him when Tsuna asked- no, commanded Reborn to trust him.
"It seems you really do have a one-of-a-kind kind of mask, Tsuna." he commented with a smirk, knowing full well that Tsuna gets what he was referring to.
"Yeah," Tsuna answered, a soft smile playing on his lips. "I guess I do."