Umineko no Naku Koro ni Shi: Forgery of the Purple Logic

Umineko no Naku Koro ni Shi: Forgery of the Purple Logic is a manga-exclusive series by Kurumi Suzuhiro. The story expands on the use of the purple declaration introduced by Bernkastel in Twilight of the Golden Witch. The red truth still applies in this game even though there are lesser than usual games. Knox's rules are stated in red to show that it is valid in this game. The story takes place outside the main story.

(Source: Umineko no Naku Koro ni Wikia)