Shinobido
Long ago, there was a dying leader. He called his son and his star pupil to his side, and told them that when he was gone, one of them would be the next Daimyo. The two were put to a contest to determine the successor. For three days, the son of the dying leader and the star pupil fought, engaging in numerous tests of ability and combat. They were evenly matched until the third day the star pupil of the dying leader used a forbidden technique, taking the son of the Daimyo by surprise, and defeating him.
The pupil became the Daimyo, and the last Daimyo's son was to be exiled to the land across the sea, to an empty land of rocky, infertile soil, and dangerous creatures. The son had his followers, though, and they became known as the Loyalists. They followed the Shadow Daimyo, who escaped his exile, and planned to destroy the Daimyo.
For five years, the land was marked by civil war, the Daimyo and the Shadow Daimyo battling each other whenever their forces encountered the other. Hundreds died. The Shadow Daimyo was eventually captured, and he and his Loyalists were all exiled to the land across the sea. The Shadow Daimyo himself was bound by seals to never set foot in the land again, or his blood would boil.
This is the origin of the Land of Shadow. Now, 30 years later, the Shadow Daimyo seeks to return to his home nation, and reclaim his rightful title. Having been pushed to the inhospitable north, he uses the very forbidden techniques that trap him there, allowing his Loyalists to become necromancers and Demonic sorcerors.
A cold war has broken out between the Land of Shadow and the Land of Light. A war fought not with swords and samurai, but with information, secrecy, and the shinobi. Too often, those ninja are nothing more than children, brought up in a time of shadow wars. Forced to kill, lie, steal, and exposed to dangers and fear, many of them snap, turning to the Dark Path that their enemies in Shadow use. The lure of power is strong, but perhaps their friends and allies can keep them from the path of darkness. Or be dragged down along with them.
Shinobido is a game about children in war.
Children doing things that adults should do is a staple of the Japanese genre known as Shounen--a genre aimed at males from 13 and up that focuses on the adventures and coming of age stories of male characters. They're known for fight scenes, fanservice, and headstrong, hotblooded protagonists.
Teenagers in shounen are often fighting in wars, or traveling the world with their magical pets, fighting other people with magical pets. Whether they're pulled into a computer world or a dream world, or they're in their own world, most shounen characters face things that should effect their mental state. Too often, this doesn't happen. A character who finds himself in the magical world he's dreamed about forgets that dragons exist and can kill him, and that he's constantly being attacked and nearly killed by a group of enemies.
This game is what would happen if they were effected by the horrible things that go on in their lives, and the horrible choices they might have to make. It doesn't do away with all the tropes of the genre, but it does try to deconstruct a few of them.
THEME
The main theme of Shinobido is that of cost. Everything has a cost. Powers have the obvious cost of using Focus, but more than that, doing one thing costs you the ability to do another. Characters are expected to make hard decisions, and sometimes there is no right answer, just wrong ones.
The biggest example of things having a cost is in the forbidden techniques. Darkness is a literal thing in the world of Shinobido. It's more than evil, it's selfishness and malevolence. It's callous disregard. Whenever players use forbidden techniques, they gain Dark Points, showing them how close to the edge they are.
In the beginning, these forbidden techniques have no cost. They're cheaper and easier to use. As Dark Points accumulate, the price becomes apparent. There's a mental cost, where the character becomes less stable. There's a physical cost, where seals and markings appear on the character's skin. And there's a social cost, where characters are ostracised for their willingness to use the darkness.
Things aren't so simple, though. Characters might NEED to use the darkness. Maybe to save themselves, or one of their allies. They might need to tap into that darkness to save an innocent. Things should never be so clear cut as good and bad.
Once a character has made that jump, though, things will get harder for them in the future. They won't be as able to avoid making more jumps like that in the future, and soon they've paved the road to their own Hell with good intentions.