Picture a meeting of the X generation guardians with someone trying to help them getting along and all.
They ask everyone to write down anonymously what skills they think they can use to help the group, then they read the list of skills they have gotten and yeah, of course, it’s pretty weird cause Chrome and Tsuna, with some luck Yamamoto too, are the only ones who actually wrote something inherent and everyone else just has weird ideas about the whole thing. But sure, it’s good to be a little unusual, they knew the group wasn’t a normal one anyway, so why not? So they keep reading and
someone wrote down ‘taking care of corpses’
so the person taking care of the whole thing probably thinks it’s a joke and goes on reading, maybe complains about the jokes they have written (when actually the only not-serious one was Lambo, cause Gokudera really can make explosives and Mukuro can conjure snakes)
but everyone else knows. Everyone else knows that Hibari was serious.