Just keep in mind that Katou was inside that bag the whole night without any oxygen and with all of those injuries and still managed to survive somehow.
Anyone gonna question how he got into the punching bag, transported in the middle of enemy territory and replaced with the actual punching bag without anyone noticing?
How is this dude even able to move after getting his Achilles heel and arm completely obliterated during the tournament?
These people all have hyper-regeneration or something.