originates from japan, stems from the word itai which means pain. the reason why is because these are usually bags with a clear front displaying tons of merch from a character (usually anime). most people choose a certain character they like, a ship/pairing, or maybe even just a whole series.
did you see the group of people at anime expo with ita bags? it was wild! some person had like 5 or more pieces of the same pin!
by cactus5390 December 28, 2017