While I also not believe that a state should have the legal right to execute anyone as that can be, will be, and has been abused, I believe it is the absolute right of victims (or those who they left behind) to determine the punishment of those who wronged them up to a proportional degree with modifications due to circumstance (i.e. someone stealing because they are poor is given leniency).
How I feel about this execution is dependent on the wishes of the Kyoto fire survivors , victims, and their loved ones.