I can't show you a specific legislation that says "you cannot hold workers liable for your losses", but the proposition seems a bit absurd to me because that just seems like unlimited liability on the worker; could you sue a worker who has to take extended sick leave because they become disabled or otherwise unable to work?

Again to be clear I'm talking about contract employees 契約社員 who fall under the scope of the Labor Standards act - freelancers who agree to pay a penalty if they breach contract I'm not sure on how enforceable that would be.