Er..I swapped A and B at the beginning of the game, so maybe for other people it's their A button to back out??

This is a great start, but it doesn't really show which keys correspond to which controller icon.

For that:

Hit escape to bring up the main menu.
Select the gear icon from the right hand edge of the top row (with your mouse).
Select the highlighted Settings block from the middle of the screen.
Go down to the Game settings row at the bottom of that System screen and select the Key Config option.
Select the Key Config option again.
Select the Keyboard option from the Target row at the top.

Now you can scroll through all of the keyboard settings.

(You can back out using any of your B button options, of course...)

(Personally, I moved R stick and L stick onto my numeric pad, and made a few other changes like that so I am not going to try build a list of these things. But someone else might want to document the default settings in a Guide or maybe even this guide?)

very helpful，thank you so much

Thanks for the listing. I heard there's a button that can reveal wrong & correct dialogue choices during decisive (bad end) event which is R3 on a controller. Do you have any idea what could it be on keyboard/mouse?

Thank you so much for this! This is super helpful!

Cheers!