For me, I recognize injustice as a sense of asymmetry, and there's evidence this is an innate faculty. If someone intentionally harms me and I did not harm them first-- and there is reason to suppose we have agreed to this non-harming somehow--even tacitly-- I will get that sense of "dirty pool." My range of asymmetry tends to be fairly broad, and after a friendship is established, I wouldn't get a sense of injustice except for prolonged, recurrent asymmetries that I felt my friend could have avoided.
The degree of pain an asymmetry causes is proportional to the degree of feeling I had for the other person (if we were close, a better word might be betrayal)-- and the direct effect of their action on my life, which is in addition to the asymmetry. For instance, if someone I knew robbed me of my money, there are two issues-- the asymmetry of their action towards me -- the injustice--AND the loss of funds. I tend to mainly feel pain from the action itself if I don't know the perpetrator, even if I also am aware of the injustice of someone harming me when I had not harmed them.
Every action in an agreement has an effect of pain or pleasure, since there is no 3rd feeling of neutral. It just isn't always enough asymmetry that we will be moved to bother with it, compared to other things we could be doing. If we get obsessed with trivial asymmetries, we will test the patience of our friends, lol!