They are wearing kimono, a traditional Japanese garment. The kimono itself is the long robe-looking piece of clothing that is secured at the waist by a sash (obi). On top of that, they seem to be wearing haori - a sort of coat commonly worn over kimono robes. Additionally, some of them are also wearing hakama - a sort of pleated trouser or skirt (depending on the design - some are divided, like pants, whilst some are undivided, like a dress) that are worn over the bottom of the kimono.