Conversation so far:
Who is Nathan?
Nathan Explosion is the frontman, lead vocalist.
How long was he with the band?
first episode.
What important role did he play in the story?
Nathan is slightly more sensible than the rest of the band, and a great deal more emotionally stable.
Does he leave the band?
CANNOTANSWER.
Is there an example of his emotional stablity?
a great deal more emotionally stable, though he is still incompetent at most things in life such as the use of a grocery store or reading a cooking recipe.

Question: What other role does Nathan play with the group?
Self-contained rewrite: Which other role does Nathan play with the group aside from lead vocalist?