Devadasy

Buried in homework and awkward feelings for his childhood friend, regular high school kid Kei Anno has his ordinary life shattered when Earth gets invaded by alien war machines. Naturally, a shadowy military organization called Spirits decides he's the guy to pilot Devadasy, a powerful mecha they've had sitting around for years. The catch — and this is where it gets interesting — the mech only works when paired with a compatible female co-pilot. So now Kei is juggling the apocalypse AND figuring out which girl in his life he's most psychologically in sync with. That tension between the personal and the catastrophic is where the show does its most interesting work. It's a 3-episode OVA from 2000, so it's short and doesn't overstay its welcome, though it leans into its ecchi elements alongside the mecha action. If you liked Neon Genesis Evangelion's angle of a reluctant teen pilot carrying impossible weight, or the female-male mecha pairing dynamic from Iczer-One, there's familiar ground here. The psychological compatibility angle gives it a bit more texture than a standard giant robot romp. Go in knowing what it is — a late-90s adult-leaning OVA with mecha trappings — and it delivers a genuinely distinct premise wrapped around some surprisingly earnest character tension between Kei and the people closest to him.