The one downside, Tsuna thinks when he's six-years-old, to his secret is that it's distracting.
It's difficult to empathize with something that he isn't but he watches, takes in the way his classmates react to fingers on their shoulders or a flat palm shoving against their chest, the way their heads turn to perceived sound, the way their body spoke in a language that Tsuna tried his best to understand. Their skin is soft, malleable to the touch, easily ripped apart by his teeth and his fingers, as small as they are, and children, he realizes early, have a distinct - nearly potent - smell to them that disturbed Tsuna to no end.
It's distracting, it's so distracting that he finds himself turning to follow scents rather than seeing with his eyes or listening with his ears. Some scents are stronger than others, more pungent, more delectable, and hunger hasn't been the same since he turned five - that's one thing off his shoulders - but that doesn't make him feel less inclined to turn his head and stare unseeingly at certain directions, his nose discerning the distance from the water, the kind of materials in his classmates clothes, the amount of fuel in a car. It comes to him in unfiltered sections, snapping through his thoughts like rubber against flesh.
They make fun of him for tripping on thin air for it, they laugh at his stupid, stupid answers because he isn't paying attention, too preoccupied with the scent of a rotting cat in the back of the school. They jab their fingers into his chest when he doesn't speak loud enough for them to hear and pull at his hair when he doesn't pay attention to them. They think they're hurting him and sometimes, Tsuna has to fight down a smile because if only they knew.
(His smile is a lot like his mother's in that aspect. Knowing, calculating, cold.)
Tsuna lets them.
He lets them mock him, lets them call him names, because better that it's him who they hurt than another fragile human.
He isn't like them. In a way, it's both a blessing and a curse.