Ryu tried to regulate his breathing. He didn't even waste the energy to create a larger space around himself, it would not only be an effort he couldn't afford to put out right now, it wouldn't be easy and it would cause a disturbance that he wasn't willing to deal with.
This many kilometers beneath the surface, the pressure was off the charts, and the hardness of the rocks reflected that. The density of material in a nigh Seventh Heaven environment was already sturdy enough to withstand the battle of high level Sky Gods, let alone Ryu's fists, especially so far beneath the surface. So, he had to make do for now.
