There’s a sleepy village. A little girl lives there. She’s the usual sort of cute kid that can be found in these games. She’s innocent and unworldly, but very kind.
The village secretly plays host to a world-shaking artifact called Judgement, buried underground in some significant caverns or the like. The Big Bad of the story appears, with companions in tow. Among them is a powerful, well-built mercenary woman. Her body is partially or completely artificial, some kind of wonder of the ancient world. The village is, of course, threatened or burned.
Along the way, the girl encounters Judgement in the caves, and the mercenary soldier chases her there. Judgement’s powers are all about moral evaluation, soul storage, and many other functions - think of it like a portable Afterlife or Heaven. One of its powers is to swap bodies and souls, and the child and the mercenary find themselves exchanged.
Very shortly thereafter, the Big Bad arrives and invokes Judgement. He uses it ‘passes sentence’ on the mercenary for her crimes - intending to betray her, so he can get away with Judgement without a rival or competitor. But the innocent soul inside the body has no sins to judge. She survives in a powerful body, while the weary, jaded mercenary is now trapped in a child’s body.
Now the mercenary and the kid need to work together to recover Judgement, stop the Big Bad, and get back to each other’s bodies. The girl will have to learn to fight - she’s strong and can heft some amazing weapons now, and perhaps has muscle memory that will help her along. The mercenary will need to adapt her methods to her new body, perhaps by developing the small selection of magic she already knows, or using throwing knives and mobility instead of muscle.
They’ll have other friends and companions appear, people who in their own way were affected by Judgement or have a grudge against the Big Bad.
What will happen on their journey?