|Released|| Concept: September 12, 2011|
|Genre||Vertical Danmaku Shooting Game|
|Gameplay||Single-Player Story Mode|
|Followed by||One Thousand Joy|
Nansei Myoudokusu ~ Toxic Difficulty (南西 妙毒空 〜 Toxic Difficulty lit. Strange Poisonous Sky from the Southwest; original title 有毒難, lit. Toxic Difficulty) is the 2nd official project in Nansei.
The project was originally released as a Touhou fan-project, but was canonized as the second Nansei project with the release of Night Creatures in a Mansion. The first track in the album was released on September 12, 2011.