Looking At Viewer
The looking at viewer tag is exactly what it sounds like. Looking straight in the eye, the anime character breaks the 2D-real world barrier. The mood of an illustration can change with a waifu's soft romantic gaze or a villain's scary glare. It is easily one of the most common and popular tags on anime art boards because it instantly makes the piece feel incredibly personal.
Artists employ this perspective in many ways. Sometimes a character casually looks over their shoulder, making it feel like you called their name on the way home from school. They may point a gun at the camera with a crazy yandere look. The tag includes cute idols smiling at their fans and serious knights who seem to see through you. Perspective matters too. Artists often use foreshortening or dynamic angles to make characters appear to lean out of monitors to look at you.
The appeal is connection. It would be great to have an anime character stare at you on your phone or computer. It turns a static character portrait into an interactive one. Just moving your eyes can make the art come alive and interesting for screen viewers.