Just found out (scriptbook of the movie) that during this scene Yori texted him that he did not want to go back to their den because he would want to touch Minato again (hug him or touch his hair) and to which Minato replied that it'd be okay if he touched him again.
It breaks my heart thinking that the reason why Minato was so scared about the CT scan was because he was worried that his mother would find out there was something wrong with his brain and that he maybe had a pig's brain.
He was so nervous about his mother seeing the reports and thinking that her son was not normal.
His nervousness and the whole fiasco with the school situation resulted in his outburst.
And righfully so. In his defence, he had witnessed the way society reacts to anything that is "not normal". Whether it's the drag queen being made fun of on TV or his friends making fun of his and Yori's friendship.
I cannot imagine the pain this boy was under and the number of nights he spent laying awake, regretting and questioning things about himself.