just in case you didn't understand,

the dialogues are alternating between hakyeon and mirae.

they are in italics because the conversations are in mirae's memories.

at the last scene, mirae drink the love potion, that will clear all memories of hakyeon and will make her love the person she sees. 

she is confronted by hakyeon who has figured her out (or has finally figured out that he likes her) and opens her eyes in shock.

she sees hakyeon (the person she truly likes). because of this, none of her memories will be messed up.

but she will have an undying love for hakyeon. so, yeah.