A Meme related to Ninomae Ina'Nis' Bare Back (and occasionally, her Ass). It originates from a certain moment during a HoloMyth off-collab 3D stream, in which Ina, using her 3D avatar, briefly exposed the rarely-seen back side of her body directly at the camera. On top of that, the quick spin caused her Waist Cape to glitch and ending up in a position that have very strong impression of Wide Hips/Huge Ass, leading to a large surge of fanart focusing on her back (and her ass too). Additionally, "Ina's back" doubles nicely as a pun, as the event coincided with Ina returning from an extended break.
Be mindful when using this tag. Don't add it to every single Back Focus/Ass Focus or From Behind posts featuring Ina. The image has to be a clear reference to the incident.