malice_cannon
A collaboration of magic between Kirisame Marisa and Alice Margatroid.
Also known as the shift-spamming technique in the game 東方永夜抄 ～ Imperishable Night; when using the Magic Team (Marisa & Alice), repeatedly pressing the focus button will cause Alice and Marisa to both fire at the same time, resulting in massive damage.
Make sure StickyKeys is off though.