Akarin
Something you say to show someone they lack presence.

This comes from the anime Yuru Yuri.
Sometimes, when you see Akari, the sound effect "Akarin" is played. Then she disappears leaving behind not much more than a dotted outline.
Person A: *never says a thing, never gets noticed, always left out or forgotten"
Person B: The moment you hear "Akarin", nothing but a dotted outline will remain of them.