L FILE No. 15 is a book that was released alongside the film L: Change the WorLd. Its contents are related to the Death Note film series continuity, almost exclusively about L, and it is predominantly a photography book.
Forward - The book opens with an in-universe forward, written in English with a Japanese translation, explaining the book. This file on L is the last one left behind by Quillish Wammy, and the other 14 files before it are unknown. The file is unverified, and neither L nor Wammy's House has been confirmed as existing.
Photography - The book primarily consist of photos taken by Mika Ninagawa (蜷川実花, Ninagawa Mika) of actor Kenichi Matsuyama dressed as L. This includes L doing various activities, such as eating sweets, enjoying theme park rides, doing laundry, drinking tea, and walking through a city. It also has photographs taken on set with candy-themed backgrounds and props.
Manga - The book contains two short manga chapters illustrated by Takeshi Obata and written by Tsugumi Ohba, titled L: The Wammy's House and L: One Day. L: The Wammy's House shows the events leading up to L becoming a detective, and L: One Day chronicles the daily life of L.
List of sweets - A list of sweets is included, and each sweet is scored by L on a 0-5 star scale. Some foods that have five stars include chocolate cake, chocolate ice cream, and coffee-flavored lollipops. Foods with zero stars included buttered popcorn and consomme-flavored potato chips.
Quillish Wammy's journal - A journal log written by Watari is included, logging some events before and during the Kira investigation. He documents people such as Naomi Misora, Light Yagami, Shiori Akino, Misa Amane, and Kiyomi Takada, and references other members of Wammy's House including F, R, K, D, and P. He documents the day that L writes his own name in the Death Note, July 7th, 2006, writing L's full name "L Lawliet" and saying he has 23 days left. The last entry is dated July 10th.
- Its cover price is 2700 yen.
- The book was one of several projects released to create hype for the L: Change the WorLd film. The others include the Death Note One-Shot Special released in Weekly Shounen Jump, the L: Change the WorLd novel, and the official movie guide for the film.
- The book's official page was at www.j-deathnote.com/L/ (now defunct); see it archived.