The "mmd-vr" tag refers to a specific type of adult content created using the MMD (MikuMikuDance) software and viewed in virtual reality (VR).
MMD is a 3D modeling and animation software primarily used for creating animated scenes, often featuring characters from the popular Vocaloid series. These animations can be highly detailed, visually engaging, and sometimes erotic in nature.
When paired with VR technology, the viewer is fully immersed into this digital world, allowing them to feel like they are part of the scene or interact with the characters directly. This combination creates an even more intense and intimate experience for adult audiences who enjoy virtual reality content.