A fanfic based on O. Henry's short story "After Twenty Years." The original is in the author's notes. It's short and so good!
Devoted criminal x upright police officer, childhood friends, told through letters, lovers who fight as much as they love each other (?)
"My friend, my dear officer, don't be sad. This is my best ending: The best way to kill myself. I feel happy knowing I can write this nonsense, which will make you remember me, before I die."