Sang's In A Coma
Sang love's the boys, and wants to stay with them. The boys, however, don't love Sang like she hopes. They want a sister, a calmer, someone to give them advice, but not a girlfriend. After being told, heartbroken Sang leaves, causing a much larger disturbance than the boys thought. Leaving no clues about where she'd gone, or even if she was leaving at all, the boys can't figure out how to bring her back.
When Sang ends up at the hospital three years later, at age nineteen, the boys can't comprehend it. They're murderous for Sang being put into a coma, and wait for her to wake. She's finally back, and they want to explain. They want to try it her way.
But when she wakes, she knows nothing. She doesn't know her name, who they are, any of her past at all, or what happened once she left. The boys take it as fate, and try to tell her they known each other forever, and they share her love. When she remembers her childhood, she knows it's a lie. They weren't there. And they took her phone. Getting it back, she hacks it, and trick she can't remember knowing, and realizes nothing they've said so far is true. At least in her mind, anyway.