Well this isn't unnatural at all!
Tsuna has the weird ability to mimic the flames that he either bonded with hasn't yet (because we all know no one can resist that welcoming aura). Which, by the way, isn't that unnatural...Unless he isn't a multi-flame user...And the Vongola is left wonder what kind of species Tsuna is...(I don't own anything and the the cover photo isn't mine! [CTTO])โฆ