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.
Ichinose?
إيتشينوسي؟
Ichinose?
¿Ichinose?
¿Ichinose?
Ichinose…
Ichinose...
Ichinose?
Итиносэ?