Turns out the one spreading the rumors was Hashimoto, who did so at the behest of Sakayanagi. Shortly thereafter, Sakayanagi appears before Class C and she informs them she has evidence regarding the rumors about Ichinose.
I'm the one
أنا
Ich hatte es …
Yo…
Yo…
Par mes paroles,
Sono stato io...
E fui eu...
я взял…