The porn video tag "nier-automata-a2" refers to a specific type of adult content that involves themes or elements inspired by the video game Nier: Automata. In this case, "A2" likely represents one of the main playable characters in the game, Android 2 (or simply known as A2).
The tag implies that the porn content includes scenes, cosplay, or artwork featuring this character from the game. Such videos or images might involve depictions of sexual acts or scenarios related to the character, within a fantastical post-apocalyptic setting. This content is intended for adults who enjoy the combination of adult themes and video game references.