R² [Rise to the Second Power](2002)

Young Kenta Akagi was born and raised in the remote city of Lutzheim. Tales of faraway places, violent wars and the curious people who fought in them have reached his ears, but seem so foreign compared to his rural home. Life for Kenta is stable, safe and altogether uneventful that is, until fate decides to strike. Kenta suddenly finds himself in the midst of a battle, fighting for possession of a girl he has never met and about whom he knows nothing. He feels compelled to protect this young stranger who seems to strike fear into those around her no matter what the costs may be.

(Source: Anime News Network)