refers to a specific adult-oriented doujin (independent) work, likely a CG set or illustrated story, by the artist Hen Neko (へんねこ).
The strongest selling point of this work is undeniably the art. Sleeping Cousin -Final- -Hen Neko-
series and note that this release marks the conclusion of the story. Art Review: "Sleeping Cousin -Final- -Hen Neko-" refers to a