We also didn't know Tsurugi was something besides human until he transformed in the middle of the trial.

[But Manaka doesn't seem especially frazzled about being implicated. She just sighs, sets her elbows on her podium, and then cups her chin in her hands as she looks up toward the ceiling.]

The output of my magic circuits has been far reduced on this station. The amount of magical energy I would require to produce an explosion that was apparently so severe would be much higher than the drops I can wring out of myself now.