Galko's skin got really dark as a result of tanning.
Otako comments that since Galko's skin has tanned so much, her nipples must be dark as well. Along with Ojou, Otako yells that Galko has dark nipples.
A lie!
كذبة
Eine Lüge.
Mientes.
Menteuse.
Bugiardina!
Mentira!