The 2 sisters remind me of the smart phone isekai thing.
Taking no damage has quite the unfortunate endings if you don't have the strength to back it up. Imagine that dragon swallows you whole and then after who knows how long, it takes a massive shit with you in it. The shit pile with you in the center is so heavy you cant move. Either you stay forever to be buried under shit and the eventual sediment buildup or after a millinia you get excavated only to be captured and sold to a research facility.
Of course there are a lot of other internally trapped scenarios, I just chose that as an example b/c of the last page.