At this time I’m wondering whether putting the lower part of the kamisori blade into a (padded) vice might be able to straighten the thing back?

Unfortunately it’s not that simple. You have to overcome elasticity, which means that in needs to be bent back more than just straight, so that in plastically deforms in the exact precise way that makes it straight again after unloading. Predicting the right deformation (i.e., this exact problem) is a difficult computational dark art in deep drawing. Also, you only get a few chances, because plastic deformation leads to work hardening (it’s like you’re forging the steel locally where it deforms locally).

To illustrate the problem, you can bend a straight piece of hardened wire like a bicycle spoke and try to straighten it again. It’s almost impossible, because the exact location of your original bend has work-hardened and when you try to revert it, typically a part next to the original bend will bend instead.