Controls are a little messed up. Kinda feels like you wanted the game to be playable with one hand using only WASD, Enter and Shift, but then "B" is Esc...?
ACTION only open the menu, BACK is to go back, USE is the actual action button, SPECIAL is to access the quick access menu (registered items and field moves), and the jump buttons are to jump inside menus (bag and dex)