The main character is not Mary Sue.
She is just an ordinary girl without any great talents. She has to work hard at everything she does, and there are no shortcuts.
The first dozens of chapters basically recall the past through a photo.
Only later do we have adult feelings. (The author is slow - -|||)
Moreover, the deceiving author cannot guarantee that this is not a tragedy or a comedy, and the ending is undecided! (This is cheating)