Fue (sleepy) and Asuna (glasses) are dating. Meru (short dark hair) is jealous of their relationship and seems to be having an affair with Asuna, though that one scene might just be them as roommates or something.
From the way Remi mentioned Asuna as Meru's ex-wife I have a feeling that they are either former roommates with benefits or just ex-girlfriends (with benefits). Seeing the Mangaka history and the theme of the manga itself I really don't buy it that they are merely changing in the same room.
