1. First, hide on the east side of the central rock, staying close to it. Wait until the girls say that they found nothing.

2. When the girls decide to check the other side, slowly looped around the bottom of the rock and hide on the west side, again close to the rock, just behind Mitsuru. Wait until the girls found nothing again.

3. When the girls decide split up, slowly walk to the center gap, interact with it and select hide. Wait patiently until they decide to stop looking.

Unfortunately, you don't get anything for your efforts, but the following scenes are more amusing then the alternative with Mitsuru joking that Fuuka's detection is worthless without her clothes and Aigis muses about the difference in human bodies.