This isn't a single question, it's a series of questions. To continue the main story, you need to acknowledge that you can see the sword and know where it's located. To get the bad ending, choose options that imply you can't see the sword at all.


There are technically multiple correct paths through. Just save and try what you believe is correct, or what you believe Takumi believes is correct. The end result if you get it wrong is extremely quick.


Btw, you kinda need to play through the game more than once to get both the AA and B endings. They are both important to get the full context of the story provided by the game. In fact, in NoAH, they made it so you *have* to get all the endings to unlock the true ending.