I think relationships in general are over romanticized like atthe end of the day I’m pretty sure a good relationship is just two people who know how to hang out and talk to each other, not whether or not they can right all your wrongs or paint a picture of a thousand suns with the breath from your lungs or some shit.
being friendly with a boy you aren’t romantically/physically attracted to and him developing feelings for you isn’t your fault, nor does it mean you were “leading him on”. you are under no obligation to date him.
Even if he gets really mad about it. Remember that it’s his problem that he caught feelings. Not your problem.