The Diary collections are two short prequel/interquels/companion stories written from the perspective of two very important characters, but who have very little face time in the series. These diaries will explain some of the more vague points of the story, such as the disappearance of Maggie, and what caused Shirai's insane transformation from innocent child to crazy murderer.

dude when i first say this section i thought it said the Dirty Collections lol
then i looked again and say that it said Diary