: Indicates the 18th volume in this specific series.
If you are looking for the official guide or the work itself, you can find the artist's portfolio and authorized sales pages on these platforms: [Amania9_s_(Amanoja9)]_BEHAVIOUR_18__BBA____[Di...
The title you provided refers to a specific adult-oriented manga or doujinshi release by the Japanese artist (often stylized as Amania9). This particular volume is part of their long-running BEHAVIOUR series. Series Overview : Indicates the 18th volume in this specific series
: Where the artist shares updates, sketches, and links to new volumes. and links to new volumes.