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.
The sight of my sister's smile 
temporarily alleviated my guilt.
منظر ابتسامة أختي أزاح عنّي
حسّ الذنب مؤقتاً
Al verla sonreír,
Al verla sonreír,
À la vue de son sourire,
Ver o sorriso da minha irmã aliviou
temporariamente a minha culpa.
พอเห็นรอยยิ้มของน้องสาว