Natsu has been hit with a black magic spell that slowly consumers his soul so the caster has half of his magic power. Gray is handed the duty of taking care of Natsu while he's in an expressionless state as Mira and Makarov search for the Caster to stop him and return Natsu to his original state. Gray is face with many obstacles but still goes through them for the one he's loved...Natsu. Btw the title is Believe in myself because I love the opening Believe in Myself how's its basically just Natsu and Gray. But I love the music too.