Collectively, they are the many tiny girls who appear in the equipment cards (and presumably operate them) in Kantai Collection.
Several of them, especially the more recent ones, are look-alikes of certain ship girls, as they represent their signature equipment. For example, The fairies of the Type 32 Surface Radar Kai resemble Ise and Hyuuga. Alternatively, the Skilled Lookouts fairies resemble Ayanami and Choukai.
