Third season ruined it all.

One of the best animes to get people into anime and one of my all time favorites.

(from my old collection of anime reviews circa 2003)

Comedy sci-fi mecha action. Mecha pilot/undercover operative Sagara Sousuke works for the highly advanced vigilante organization Mithril, which operates from a submarine carrier. He is tasked with defending Chidori, a high school girl with an unkown hidden potential who could affect the balance of power. The beginning of the series, which concentrates on high school silliness and the mismatch of the romantic interest, works far better than the serious parts, or even the later comedy. Towards half way it just loses steam, and the animation gets a bit lazy. Part of the problem is that the back story and world aren't that well developed, so there's little reason to care about the serious stuff. The mecha fights aren't that interesting (knife fights??). Continued far more successfully in Full Metal Panic: Fomoffu.