Look; I'm dumb. How is this a wardrobe error? Is the strappy bit legit the backside?
She's wearing it backwards. This is a drawing of a scene in chapter 59 where she is trying out swimsuits and Assistant hands her that one because he thinks the design is pretty tame, as the strings there are on the back part while the front is like a usual one-piece. Senpais screws up wearing it.
