I Sowoneun Chwiso

A long-time shut-in, Ramiele gets pressured by her mom to attend a banquet where it just so happens that her crush, Tyriel, and her ex-best friend, Beryl, announce their engagement. “If only I were Beryl!” Ramiele wistfully thinks. Her necklace suddenly lights up at the thought, and she is transported back in time to her days at the academy, but as… Beryl?! Stuck inside Beryl’s body, she at first wonders how she can live up to Beryl’s reputation, but when Ramiele meets her own self, she learns more about herself than she ever had before.
(Source: Tapas)