Keep You Like An Oath (слэш)

The kid, sounding possibly more indignant than anyone Bucky’s ever heard before says, “It’s not like I throw the first punch! I just maybe, possibly, throw the second.”
Bucky thinks three things:
‘Oh shit, that’s my soulmate.’
 ‘Jesus christ, maybe don’t use your face as a fist if you’re gonna punch people.’
 And ‘Oh my fucking god, that’s my soulmate.’
 
In which everyone is born with the first words they'll hear their soulmates say written on their skin, and of course Bucky and Steve are each other's.