Sana didn't like Tzuyu's girlfriend. Sana and Tzuyu are childhood best friends, during high school Sana and Tzuyu were friends with benefits. Sana had feelings for Tzuyu but didn't say anything because she didn't want to ruin what they had and besides, Sana knew Tzuyu liked Park Jihyo. In university, Tzuyu and Sana are dorm mates. Tzuyu announced that she is dating Jihyo and that they'd be going on a date. That's when Sana's mastermind plan to make Tzuyu hers came into action.