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.
Did you tan in a swimsuit, then?
حصلتِ على السمرة في ثياب السباحة؟
Oh? Hast du dich dann
im Bikini gebräunt?
Entonces, ¿te bronceaste 
con un traje de baño puesto?
Alors, t’as gardé ton maillot ?
Ça fait des marques, non ?
Quindi ti sei abbronzata in costume?
Ti sarà rimasto tutto il segno!
Pegou o bronzeado de biquíni?