Similar to a hawaiian shirt, a kariyushi shirt is a collared, short-sleeved, patterned dress shirt mainly worn in summer. The shirts are made in Okinawa to promote Okinawan tourism. Kariyushi shirts often have designs based on patterns found in Okinawan art, motifs from things common to Okinawa like bitter melons or dragon boats, or shiisaa-patterned designs.
This tag will most likely be associated with Komano Aunn, as her default outfit is a red komainu-patterned kariyushi shirt.