I can't live like this

Gray Fullbuster and Natsu Dragneel have always hated eachother and been bitter rivals.
But one day when there class goes on a field trip to a museum, natsu and gray are paired in a group
And when they started to fight they knock over a mummy and purple light comes out
They think it's nothing at fight and ignore it
But when they are home that night
They aren't themelves anymore...