Sorry that's my bad when I said enough being snarky I was referring to myself I didn't assume you were being snarky.
As for the argument that they lack a cost because they are natural one doesn't really hold up. Looking at summoning in the past. For flight there is a castle that flies in the roshomon contract, a spirit that flies in good help is hard to find, kitsune that can fly in the hyakki contract which are also spirit kitsune, and an eel that lacks wings in the eel contract. So flying without a flight based limb or booster has occurred in half of all contracts that include flight.
The sensory is based on their ghostly nature and is a power that exists in mythology. But if you don't like it I can easily change it to something more traditional even if it makes less sense.
As for ghosts and spirits in Naruto
proof that ghosts exist and can be summoned
yokai (auto correct was a pain lol) means ghost
ghosts inhabiting stone
someone who's soul was sealed away and was a demon
a ghost poltergeist
a corpse crab
Naruto is full of spirits and poltergeist these are some of the lesser known examples, but spirits and demons make up a decent number of approved contracts.
As a note of all the contracts listed majority can fly at no cost.
Note: after thinking on it the ability to float objects unencumbered within 6 feet of the user i picked because its a ghostly thing to do, but if it is really that much of a stretch I am willing to put an additional cost to it. How about a E rank cost (none) for 5 pound objects D rank stamina cost for 10 pound objects, a C rank for 50 pound objects a B rank for 100 pound objects, an A rank for 150 pound objects and an S rank for 250 pound objects. with the item limit dropping for each rank of object.
average lets them carry 1 E rank object
proficient lets them carry 2 e ranks or 1 D rank,
Masterful lets them carry 3 e ranks, 2 D ranks, or 1 C rank object,
epic lets them carry 4 e ranks 3 D ranks 2 C ranks, or 1 B rank
Legendary 5 e ranks, 4 d ranks, 3 c ranks, or 2 B rank, or 1 A rank
Godlike 6 e ranks, 5 d ranks 4 c ranks, 3 b ranks, 2 A ranks, or 1 S rank