Well, that was somewhat clever for your average escape attempt history in this manga to be honest, was expecting him to mess up stupidly and get his ass saved by Nishiyama haha
Not sure what they will do against the Fish Demons tho, pretty sure it is an utterly impossible obstacle that serves as a major reason no one even attempts to escape any longer. And since they saw those monsters themselves, they should be aware of that much themselves, Ryousuke is not thinking straight, if anything him panicking trying to leave could get his love interest killed rather easily (though as for him, I'm pretty sure he has some plot armor at least for now).