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/I suggest this: this thing is probably like a deep well. Let Tsukiko approach the edge and throw something edible into it (even an apple core, or whatever can be found in the sewer that homeless people eat). She should throw it right at the edge, preferably so it gets stuck against the wall but falls into the water. And she should get ready to strike.
Livia approaches Tsukiko from behind and prepares to cast a spell./