okobo
Thick, blocky sandals that are (traditionally) worn by geisha during their apprenticeship. The most notable variety of okobo that crop up in fanart are the black-lacquered type with red straps.
(Technically, the black-lacquered finish is only worn mainly during summer, and the color of the straps used changes depending upon how far along the apprentice geisha is in her training)
Notable wearers: Onozuka Komachi