Title: Fighting Perfection
Author: shawolistic
Genre: angst, romace, slice of life
Length: 15 chapters 
Characters: Sehun, Kai, OC
Status: Completed

Summary:

"Compared to the bright blue summer sky, she thought she was the dull grey winter clouds. Compared to the crystal clear waters of the river, she thought she was the murky waters of a neglected pond. Compared to her dazzling younger sister, she thought she was just a silhouette of a figure, which would ultimately submerge into the approaching darkness."

Why I like it:
slice of life, i read this story twice and i still cried
disclaimer: this story is not exactly a sehun-centered but u guise should still read it