Or in the Japanese Mahou Shoujo Lyrical Nanoha. (I think. Correct my spelling if I'm wrong, 'kay?)

Nanoha stars Nanoha Takamachi, a fairly normal third grader who luckily (or maybe unluckily) rescues a magical boy named Yuuno from a artifact called a Jewel Seed. Yuuno gives her a magical gem called 'Raging Heart' which Nanoha discovers helps her tap into her magical potential, which she uses to capture the rampaging Jewel Seed.

So far, it sounds like your typical magical girl show... until Fate Testarossa arrives. A sad eyed blonde haired girl she also wants the Jewel Seeds for her own reasons and fights Nanoha. Nanoha, on the other hand, is fascinated by Fate and wants to know why she's so sad. From her introduction the focus of the series becomes the rivalry between Nanoha and Fate, as well as the mystery of Fate's background. No spoilers but Nanoha eventually wins Fate over and ultimately saves Fate's life.

Magical Girl Lyrical Nanoha A's takes the existing subtext and ramps it up even more, with long scenes of Fate and Nanoha staring into each others eyes, spending time together and generally being very cutely romantic. Amusingly the 'afterward' set six years later features Yuuno confessing to a mutual friend he's made no progress getting Nanoha's attention. Gee, hinting much? *lol*

Both series are available through Geneon/Funimation and I'd recommend them both. ^__^