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I have two ideas, Ney:
1) Cast the spell. It's cheap, and even if the monster doesn't die, it will be paralyzed. Although, it doesn't seem very durable. The downside is that if paralysis/death doesn't prevent control, Libya is doomed. The upside is that Tsukiko won't be harmed.
2) Use the fire storm. Here, we'll kill the manipulator and Tsukiko. The chances of hitting her are, of course, minimal, but they exist. This option is more reliable in the sense that if the control doesn't wear off, the crazy Nihonko will be dealt with. The downside is that you'll have to eat two pieces of cake. But honestly, I like this option more.
Added 10 minutes ago
In short, I'm in favor of the fire storm.
Added 48 seconds ago
Of course, there's also the option of freezing Tsukiko/levitation, but it's not very good. It consumes a lot of mana, and you might be controlled.
Added 5 minutes ago
Revan said that Draerian control wears off if the caster is killed. I think the mechanics are similar here. But I'm still in favor of the storm.