What do you do when you know you're going to be attacked by a good girl? Carry the power of a slut with you! Aya's attack sees off Sanae before the pretty tough battle even begins.
This bug works on all bosses that have midstage dialogue; presumably ZUN programmed the damage engine to treat them like normal enemies that could be destroyed when attacked enough. Only the Reimu C and Marisa B bombs deal damage fast enough to destroy the bosses.
You will receive 11,770 points and a single power item after destroying Sanae.