Usually, eating something strange causes hallucinations. Or... not eating for a long time, so whether Yusuke ate anything recently may not narrow the problem down as much as Hifumi would hope. If she can ever get him back on the topic, anyway.

"Well, I don't know what precisely, but one minute everything was fine, and the next it was raining... possibly blood and there were bones bursting out of the ground. The really strange part is that most people didn't even seem to notice."