Flashback

Somehow the main character here realized how to go back to the past by visiting her memories at the time of death (when your life flashes before your eyes, supposedly) and then just slow her breathing (?) and living in the memory, so then she can change the future (actually, the present - it's only the future in the POV of the memory).

Why does she need to change it all the way back from the very beginning and in such a drastic way and not right at the point where the tragic thing happens, is also beyond explanation.

All of that nonsense wrapped up in a wannabe cute and quirky love story. Empty and silly.