When he finds her walking alone after being attacked by bandits, he vows to be her protector. A sweet guy, even if he's a complete moron. In my opinion, Gourry is supposed to represent the audience of the show. He's always confused and asking questions about the plot. We also have Zelgadis, a man who is cursed, and now part golem and demon.
Amelia is the super-cute member of the team, introduced about halfway into the series.
As does her father. Finally, we have Sylphiel, a wizard who excels in healing magic and has a major crush on Gourry. The characters really make the show. You'll always get a smile when Lina is about to clobber Gourry, when Amelia leaps up to a high vantage point in order to scold evil-doers and when Zelgadis gives a tired sigh because he's weary of traveling with a bunch of freaks. The plot, as mentioned above, is ever-thickening.