Rumia's battle plan:

There was also a plan to fire off every spell card at once as soon as the curtain opened, but it was rejected by Rumia.

What if our spell cards are canceled out by Kazami Yuuka's spell cards? After that we would have to fight against Kazami Yuuka without any spell cards at all.

On the other hand, what happens if Kazami Yuuka runs out of spell cards?

It's been asserted that Kazami Yuuka has only three spell cards

And

Rumia had a thought concerning one of these, the Master Spark:

"For some reason or another, Kazami Yuuka doesn't use Master Spark. Or rather, she can't use it."

But, outside of Hakurei Reimu and Kirisame Marisa's account of Kazami Yuuka's Master Spark (or to be precise, a danmaku pattern that resembles Master Spark), eye witness reports concerning it

If that weren't the case, it stretches the imagination to say she just doesn't use Master Spark, no matter how strong the opponent, given her belligerent personality.

Of course, this was all Rumia's reasoning, there was no proof

But, if it were true, then they had to take advantage of it before anyone else figured it out.

If they did this after someone found proof, then it didn't seem likely that they would be able to overturn their reputation as idiots.

Five mice defeating a cat wasn't enough.

Now that she saw the possibility, there was no time to waver.

Now was the time to gamble.

The defiance of the weak, mocked girls

Starts now.

Alright then --