A whole bunch of freckles! Marco's not quite as tanned as Bertolt, but he more than makes up for it with the freckles that literally cover his shoulders, arms and back. Plus, there's no chance to feel self concious about it, not when Reiner is kissing his neck, and Bertolt is practically petting his shoulders.

He grips his hands a little tighter against them, wanting them closer. Then he splutters a little, shoulders shaking.

"I don't care - this isn't any of Jean's business!" he's not going to deny that Jean has some kind of weird possessive streak involving Marco, but it really isn't his business.