"Belldandy" is a reference to the character Belldandy from the Japanese anime and manga series, "Ah! My Goddess." In this context, it would be classified as a tag in a porn video that represents a specific character or theme related to that character.
Belldandy is a goddess who descends to Earth to complete a mission, and during her time there, she encounters a young man named Keiichi Morisato. The two characters form a deep bond throughout the series, which often includes romantic themes and elements of fan service, such as suggestive or revealing clothing.
Therefore, the "Belldandy" tag in a porn video implies that it features content centered around this character from the anime and manga series "Ah! My Goddess." This may include scenes with her interacting with other characters or engaging in explicit sexual acts, but the focus remains on the presence of Belldandy herself.