The way it seems to work is Start each battle with a full cup At the beginning of each battle turn, draw the Japanese battle plans. At the end of the battle turn, put them aside, do not return them to the cup.
If you ever run out, you fill the cup again in mid battle.
All the above is correct. I'm only chiming in to point you to more conversation on the topic if you're interested, as this same question was asked last week, so it's had more time for input: Japanese Battleplans