Axia's character design has black nails so it's likely that the translation should be along the lines of "(Your) black nails are really pretty" as OP pointed out. Kronails is probably a mistranslation due to me pushing a pun. Krone is spelt クローネ (ku-ro-o-ne) with an extended vowel after the ro, and listening to it again he didn't extend the vowel so it's likely to be kuro (black).
I love how they are completely opposite of each other. Lauren is overall smaller than Axia, but Axia is prettier and cuter even though he is bigger. While Lauren is more of a handsome and cool guy type.
I was expecting something else, please my dirty mind, get out of here xD I just love that Lauren just couldn't accept it fully that his hands are smaller lol
Thanks for the translations ❤️ without sub I only understand that they comparing their hand to each other and axia's hand is bigger than lauren, nothing more than that but I can totally imagine and ended up squealing inside. After I see this my heart goes brrrrrrrr