Slaves, or..?

What does she mean fishbones?! he has cracked many of his bones but that could be because of a beast attack or something else

After hearing the girl's strange words, he immediately activated his spiritual sense and pour it all on her body, and immediately stopped chewing his food in stupefaction...

Her bones are at least two or three times more dense than his own and they take up more space in her body than his, her skeleton makes up at least 60% of her entire body in size, and represents about 90% in terms of mass and weight!

Not only that, but the number of bones in his body is also higher, especially in the areas of the body's joints 

Her spine in particular is extremely strong, with this structure and toughness, it can be compared to a steel pillar! 

Seeing her bone structure, it was not strange if she called him fishbones!