The phrase refers to a high-definition or remastered release of the 1990s Japanese adult animated (hentai) series Haitoku no Kyoukai
In the visual novel community, "Extra Quality" is not an official subtitle from Empress. Instead, it emerged as a for the highest possible preservation standard of the game’s assets. When users search for "Haitoku no Kyoukai Extra Quality," they are typically looking for: haitoku no kyoukai extra quality
Here’s a detailed breakdown of the (also known as Haitoku no Kyoukai: Extra Quality or “Boundary of Depravity – Extra Quality”), a well-known Japanese adult visual novel by Empress (a brand of WillPlus). The phrase refers to a high-definition or remastered