Some people run away from things that scare them, and some people are scared of things that they don't understand. [Though it's interesting that apparently Minato didn't mind the first kiss.]

You're also in a giant ballroom full of people and didn't really give him a warning before you told him how you felt. Maybe he was just blindsided. My first instinct when I told Ruby I liked her was to immediately stop talking until she dragged me out of my own head so...[A shrug.]

Basically? Feelings are pretty dumb but that doesn't make them any easier to understand. And it doesn't make them any less real. I really don't think Minato would say he didn't mind if he actually minded. He can actually be a blunt jerk sometimes.