Warui ga Watashi wa Yuri ja Nai

In an attempt to win her homeroom teacher's heart, Itsumi Toudou purchased a shady love potion, and tested it out on her stuck-up student committee president, Yomotsuka. Now, she has an uncharacteristically affectionate girl to deal with, and she's not even a lesbian! Right?

(Source: MangaDex)