Fic: Five Times Steve Rogers Had No Self-Preservation Instinct and One Time It Was All Bucky Barnes's Fault
Captain America (Movieverse)
Steve needs certain things that Bucky's willing to provide. He doesn't always understand why Steve needs it, but he understands that he does. And Bucky gets something out of it too.
And he knows the real reasons Steve needs it as badly as he does.
On AO3