User blog comment:IamJakuhoRaikoben/Chapter 337: The Golden Plains, Review./@comment-4449950-20130628130250/@comment-7418318-20130628134925

The way I saw it, Haru didn't flip about about Lucy kissing Elie out of jealousy. He was angered by Lucia doing that to Elie without her assent and because it made Elie cry (much like Natsu flipped out when Jellal made Erza cry).

So I wouldn't necessarily say that's the point where it all started.