Why sit there and take more damage when you can blow them away right now? Here's my idea:
Tenshi retreats.
Murasa moves up and kills 12.
Alice hits 11, then Reimu finishes.
Kogasa visits Kourin.
This just leaves #10, who can't kill either of you in one hit.
As for my side, is it agreed that I should take myself down to 1 HP to give Youmu or Cirno the kill? Because if that's what you really want, I'd be willing, unless Alpha Team gets shafted by the RNG.