Luke is a spoiled prince of a fairly peaceful kingdom. One day during a sword lesson, a woman tries to attack his teacher; for reasons that aren’t immediately clear, Luke and the woman are teleported some distance away. There he starts to learn of a threat to the peace of his and other kingdoms, and possibly even to all life.
The fact that this is derived from an adventure game – with members joining your party, boss fights, side quests etc – is so blatant that one enterprising fansub group uses the game’s stylings for all magical attacks. It also has the gamelike habit of inventing pieces of jargon, based on resonance and music: “fonic arts” for magic, “fonon” for innate magical attributes, “fomicry”, “fonstone” etc. It even has a chibi mascot. But get beyond that, and the plot is actually quite decent.
The world Luke lives in is one in which everything that happens was predicted long ago. At the start of the world, its future history was recorded in The Score, a series of crystals which can be only be read through magic. Rulers and magicians across the world consult The Score to guide their decisions, to go to war or to make peace, to rule magnanimously or cruelly. The truth of the score is confirmed for the main characters when it predicts that a rescue mission will result in a larger disaster. Luke impulsively decides to attempt the rescue anyway, and it does indeed bring the disaster. The main plot involves an incredibly audacious scheme for breaking humanity free of the percieved curse of The Score.
Due to losing his memory at a young age, Luke hasn’t even the experience due a normal teenager: he’s childish, impulsive, weak, and honestly a bit of a Shinji. He’s also far from the strongest fighter, so it’s a bit of a mystery why he’s treated as the leader of the party, but he is and he must grow up to meet that role. He gradually turns from a kid with all the privileges of royalty, into a man able to shoulder the resonsibilities of leadership and make hard decisions that will affect the whole world.
The story is willing to do the hard things: to have the heroes fail, to kill primary characters, to develop good reasons for the bad guys. There is more depth to the series than initially seems to be, and it’s worth getting sticking with it to see it develop.