It doesn't have to be sadomasochism, but it must be sad enough.
Personal recommendation:
Chapter 1 [Meeting my wife at the age of eighteen]
Chapter 4 [His name is Jiang Nan, my name is Jiang Bei]
Chapter 8 [He owes me a wedding]
Chapter 9 [Zhijiao promises life and death]
Chapter 10 [That summer when we were just friends]
Chapter 12 [She doesn't know what liking means]
Chapter 14 [Swallow Returns to Nest]
Chapter 15 [Agarwood Pillow]
Chapter 16 [Shen Liuzheng]
Chapter 31 [Butterfly Silver Bracelet]
It's so cruel, but so beautiful!