Allow me to summarize the plot of the series as if I were Christopher Walken and I had to play through them all in a one-go-marathon:
You see... There's this kid... And this kid has a key sword. He fights mansters with his keysword... With Disney animals...For light... Then he forgets everything, in a castle and remembers again... After he goes.. To sleep.
Then there's another kid who uhh.. Has dreams about that other kid. This other kid... Can ALSO use the same key sword... Long story short... This.. Kid fights mansters too. Then he finds the first key sword kid... First kid... Wakes up.
But while uhh the... First kid is sleeping... The other kid... Was actually, in a mob, and they collect hearts. He leaves the mob because his friend, disappears.. He finds and fights with his friend... And, she disappears, for good
But, way before those kids... There were three teenagers, that also had key swords. They get separated Because uhhh an evil, older man comes along... Lies to them. Nasty stuff. Old man posses oldest boy in the group... He is the bad guy for every other game... They're all connected..
The first kid he, goes in a book.
The first kid and his friend... They, go to sleep and fight uhh.. Mansters in their sleep. Main bad guy can... Travel, through time.