"It's all to target those non-human classmates."
"Once you inform the Security Guard, they should enter through other passages. If they find non-human classmates, they are likely to deal with them just as they dealt with the sculpture last night."
"Moreover, if the Transformation Pathways I've deduced don't have any major issues, then they may exhibit characteristics similar to sculptures when their layers are disturbed. For example, when they're attacked by a Security Guard, the blood from their wounds might turn into tomato sauce, and their limbs may become plaster-like... and other such illogical transformations."
"Therefore, to prevent cognitive issues after we witness such things, the Cafeteria rules include the following sentence:
[If you choose to report to the Security Guard, please leave the Cafeteria immediately after doing so. Do not stay behind or be curious about the Security Guard's subsequent actions.]
