This manga was illustrated by Toshifumi Kobayashi (information on him is nigh-on non-existent), and was released before her official debut. In addition to the manga itself, this book contains a good amount of bonus content, such as a ‘day in the life’ feature, an interview, and some self-portrait doodles by Yukiko herself.

A series of essays written by Yukiko Okada herself, published by Wani Books. Yukiko mostly writes about a variety of personal anecdotes (such as her experience as an extra in Chuugakusei Nikki) and personal thoughts (such as her love of stars.) Also contains some extracts from her personal diary (which would later be published in full in Ai wo Kudasai.) Although not a long book, this is a must-read for fans interested in what Yukiko had to say about herself.

A tie-in to Namiko, Yukiko and Saori’s Doki Doki Radio. I don’t have much information on this book - it hasn’t been uploaded online and I have not obtained a copy for myself.

This appears to be one of the more obscure Yukiko Okada related publications, and it goes for a hefty sum second-hand these days.

As per the title, this book is an in-depth exploration into the reasons behind Yukiko Okada’s death. Written by journalist Toshiaki Kaminogou, this book goes into a surprising amount of detail. There are a lot of interesting nuggets of information and interviews with people who knew her, all helping to build a more complex picture of Yukiko as a person. While some details are of questionable authenticity, this is a valuable piece of research, and is notable as one of the first major publications to challenge he notion that she killed herself purely out of love for Minegishi.

Arguably the definitive resource on Yukiko Okada (and the only one of these books I pysically own.) This book is split into two parts, the first being a long, insightful essay by Yukiko’s mother, Takako, about Yukiko's life and personality. The remaining pages are dedicated to reprinting her artwork, poetry, and diary. The morality of publishing Yukiko’s diary is questionable but given the media’s speculation of her private life, the choice is completely understandable.