People loitering around outside classes isn't unusual. But someone sniffing a poster definitely is.

Maybe it's some kind of scratch-and-sniff thing? Tamaki remembers when people would have scratch-and-sniff stickers, or scented markers in school. Unfortunately, smell is a sense long lost to him, but, out of boredom, he comes closer anyway.

If Amethyst can see ghosts, she'll see a teenager staring at her, staring at the poster. If she can't, she might notice it's gotten a bit chilly suddenly.