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'd initially intended to simply 
wait and watch what happened.
نويتُ الانتظار ومشاهدة ما يحصل
فحسب في البداية
Eigentlich wollte ich
diesmal nur zusehen.
No tenía planeado intervenir
en este incidente.
No tenía planeado intervenir
en este incidente.
J’avais l’intention de rester spectateur
sur cet incident.
Avevo intenzione di stare in disparte
a osservare come si sarebbe evoluta la situazione.
No início, eu pretendia só
esperar e ver o que acontecia.
Изначально… я не собирался
вмешиваться в ваши разборки.