What are the literary masterpieces that describe unrequited love or unrequited love, except "A Letter from a Strange Woman"?

One of the founders of Taiwanese online literature, Ruffian Tsai's "First Intimate Contact" is the beginning of online streaming literature. (Telling the story of a girl who has a crush on a boy)

Words about unrequited love or secret love are usually found in poetry. Most orthodox literary classics reflect the current social situation and satirize the ugly reality. Very thoughtful and rigorous.

The rhythm of the poems is cheerful and lively, and often contains a lot of emotions.

For example: Xin Qiji's "Love Jade Case Yuan Xi" is about the poem that the author wrote when he saw a girl on Yuan Eve and was heartbroken

Guan Guanju in "The Book of Songs" Dove, on the island of the river, there is a graceful lady, and a gentleman is fond of fighting.

"Mistake" by Zheng Chouyu

I walked through the south of the Yangtze River

The face that waits for the seasons is like the blooming and falling of a lotus

If the east wind does not come, the catkins of March will not fly

Your heart is like a small lonely city

Just like the bluestone street facing the evening

The sound is silent , the spring curtain of March is not lifted

Your heart is a small window tightly closed

My dada’s horse hooves are beautiful mistakes

I Not a returnee, just a passerby...

Emotions are mostly seen in poetry, while orthodox literature is mostly seen in reality