Manga
Timeline ┃ Reading order
The main manga. The current fan translator is 
The manga adaptation of the BEAST light novel, illustrated by Hoshikawa Shiwasu. Completed.
The manga adaptation of the Dead Apple light novel, illustrated by Gunji. Completed.
The manga adaptation of the Gaiden light novel, illustrated by Oyoyo. The current fan translator is profqlasses. Ongoing, with frequent pauses.
The manga adaptation of the "Dazai, Chuuya Age 15" light novel, illustrated by Hoshikawa Shiwasu. Completed
The manga adaptation of the "Storm Bringer" light novel, illustrated by Hoshikawa Shiwasu. Ongoing. The current fan translator is decay of frost.
The manga adaptation of the "Untold Origins" light novel, illustrated by Tomori Adachi. Ongoing. The current fan translator is decay of frost.
The manga adaptation of the "The Day I Took In Dazai" light novel, illustrated by sorakura. Ongoing. The current fan translator is decay of frost.
The manga omakes are 2 page bonus comics included with the each volume.
The DVD Omakes are 2 page bonus comics included with the DVD sets.
Wholesome spinoff manga illustrated by Kanai Neco. The current fan translator is croatian bsd fan.
Non-canon collection of short manga stories illustrated by guest mangakas/fans.
Side comics that don't fit into any other category.
Light Novels
Covers Dazai's entrance exam for joining the ADA, written by Asagiri Kafka.
About Dazai when he was 18 in the mafia, written by Asagiri Kafka.
Contains 2 stories, one about the ADA coming up with Atsushi's entrance exam, and one about how the ADA was formed, written by Asagiri Kafka.
Side story that takes place after the anime's season 2 (or after chapter 37), written by Asagiri Kafka.
Covers the events of the Dead Apple movie, written by Hiro Iwahata.
Takes place in a darker "alternate universe", written by Asagiri Kafka.
About Dazai and Chuuya when they were 15, written by Asagiri Kafka.
About how Chuuya got his hat, written by Asagiri Kafka.
About how Dazai met Oda, has a side A and side B, written by Asagiri Kafka.
About characters based on authors who are still alive today, written by Asagiri Kafka.
A light novel adaptation of the events of the beginning of the BSD anime written by Mari Kosaka.
Short stories written by Asagiri Kafka.
Stageplays
The stageplays are subject to frequent takedown, so I encourage you to download them just in case. All of them have fanmade subtitles, except the behind the scenes videos. If the subtitles are in a separate file, you have to add them manually using something like VLC media player.
Link
There is a lot of extra content featuring the stage actors. You can find a lot of it on bilibili, and on the social medias (usually twitter) of the stage actors.
Cast Comments
Press Conference
More Untranslated Interviews, BSD VA/Actor content
Audio
Included in Drama CD 1: Somewhat Extraordinary Days.
Audio (First in playlist; chinese subs)
Audio + Fan Translation (1)
Fan Translation (2)
Video + Fan Translation
Included in Drama CD 1: Somewhat Extraordinary Days.
Audio (Second in playlist; chinese subs)
Audio
Fan Translation
Video + Fan Translation
Included in Drama CD 1: Somewhat Extraordinary Days.
Audio (Third in playlist; chinese subs)
Audio + Fan Translation (1)
Fan Translation (2)
Included in Drama CD 1: Somewhat Extraordinary Days.
Audio (Fourth in playlist; chinese subs)
Fan Translation
Included in Character Song Mini Album Volume 1, following Dazai's song, then followed by Kunikida's song.
Video + Fan Translation
Included in Character Song Mini Album Volume 2, following Ranpo's song. No English translation currently.
Audio
Included in Character Song Mini Album Volume 2, following Kenji's song, then followed by Tanizaki's song.
Video + Fan Translation
Included in Character Song Mini Album Volume 3, following Akutagawa's song.
Video + Fan Translation (1)
Video + Fan Translation (2)
Included in Character Song Mini Album Volume 3, following Chuuya's song, then followed by Kajii's song.
Video + Fan Translation (1)
Video + Fan Translation (2)
Songs for each character, sung by their VAs, from the character song mini albums.
Playlist
Atsushi - Young Boy, Run Under the Moonlight
Dazai - Goodbye to the Attempt on Eternity
Kunikida - Unclouded by my Ideals
Ranpo - Labyrinth Deciphering Game
Kenji - The Way of Honest People
Tanizaki - Bewitching Screens
Akutagawa - From the Trembling Dark World
Chuuya - DARKNESS MY SORROW
Kajii - An Inquiry Into Irreversible Phenomena, With Specific Regard to Changes of State
Interviews
wip
Games
English version currently nearing end of service.
Wiki
Currently only available in Japan (unless you have a VPN...).
Wiki
Extra