threesome invitation
Images or animations where a third character is being invited to engage in sexual activity with two other characters, with the invitation being from one or both characters. The third character may be depicted in frame, or may be out-of-frame, and either referenced in dialog or by the attention of the characters.
This does not include couples of any combinations of genders whose attention is on each other, unless it is clearly implied that a third character is invited to join them both.