The title, "BLUE" refers to the colour of Tatsumi's eyes and various character's states of mind during the course of the fic.
"Death in Midsummer" (chapter 1) is one of a number of short stories by Mishima Yukio.
I don't know exactly when Tsuzuki and Tatsumi were partners, so 52 years ago is my own guesswork - correct me if you know the facts! The past case mentioned is inspired by volume 5 of the manga, but the bereaved mother, Sugimori Etsuko, is my own OC.
The approximate timeline for this fic is sometime post-GenSouKai, hence some aspects that would seem OOC during the course of the anime are my own interpretations of character development. I have unfortunately had to ignore the current (Kamakura Hen) chapter of the manga in this fic as I have no idea where the stuff about Hisoka's family is leading, nor the repercussions it might have.
Chapter 4 contains a reference to Kurikara being Hisoka's shikigami. At this point in time (April 2003), I have absolutely no idea whether or not this will happen in the manga. Own assumption/guesswork ahoy!
Also please take note of the NCS warning at the top of chapter 4.