how can i get the seret ending on bbs

we don't know its not out any where else but Japan yet. But most likely if you go through proud or (the newly featured) Critical mode, just as normal, with all three characters then you get it after the last character's story you play through. If you play normal or beginner mode though you'll most likely have to do EVERYTHING in eat story(including collecting everything there is to collect and beating everyone there is to beat like special bosses and non-mandetory fights and events). It's alot easyer if you start with the hardest dificulty to begin with, because to be truthful the enemies have the same exact moves almost everytime no matter what dificulty you're on it just make them harder to read and predict.

KeyofVentus is right, if you do proud or critical mode you will just have to go through Terra, Aqua, and ven's story in the right order. But if you do beginner or medium mode you will have to do everything including getting ALL the xehanort reports. So pretty much it's better if you do proud or critical mode.

In Beginner Mode you won't be able to unlock the secret ending, only on Normal, Proud, or Critical Mode. For Normal Mode you have to basically complete every aspect of the game in order to unlock the secret ending. It is only in Proud & Critical Mode that you'll be able to just go through the story without having to do much to see the secret ending. If you don't like doing work then I caution you to not do normal mode & do either proud or critical mode because aside from putting in more hours of your life to complete the whole game, you'll most likely have to defeat the super-hard optional bosses in order to see the secret ending. But, if you are the type to get the most out of the game then go the opposite of what I've previously said and do normal mode.

i thought there was no secret ending in bbs