Both leads have past relationships. Two female leads, no major romantic storyline with male characters, neither protagonist dies, and neither protagonist marries a man.
A secret crush comes true, with a long romance that stretches from school into adulthood. Rather than a story about the love between two protagonists, I prefer to call it the personal growth journey of the heroine, Shen Qi'an.
From student life to becoming a celebrated Best Actress; from being a nobody to being noticed by the person she has a crush on; from loving someone to learning how to love someone; from obsession to letting go. Step by step, she becomes the best version of Shen Qi'an.
The story is filled with foreshadowing that takes careful reading to uncover. The pacing is very slow, and the emotions are expressed subtly.
There is no perfect romance here, only the helplessness and cruelty of reality.
As for whether it's a happy or sad ending, I don't want to define it. I'll leave that to the readers.
Theme: Some encounters make the years shine, yet still can't withstand reality. Loving each other doesn't necessarily mean staying together.