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.
They're not retracting inward at all!
إنّهما لا تتراجعان للداخل إطلاقاً
Die wachsen nicht nach innen!
¡No los tengo hundidos!
Mais j’ai pas
les mamelons rétractés, moi !
Ma io non ho mica due mele sul petto!
Os meus não estão para
 dentro coisa nenhuma!