In March of 2004, a large-scale revolving door, at an entrance of a commercial building in Roppongi, Tokyo, caught a boy by his head. It was fatal. The author privately initiated "The Door Project" to investigate the cause of this tragic accident. The study identified that the door was driven by two motors and stopped by four braking wheels triggered in case any of the seven types of sensors tripped; the basic concept was artificially-designed safety. The author, with others that joined the project, build a crash dummy to recreate the jamming mechanism and found the jamming force to reach about 6,000N. We learned from our further study into the product evolution that the original European design concept to keep large revolving doors at light weight for safety was lost in Japan and replaced with shiny and gorgeous looks. People involved, i.e., designers, owners and managers, were preoccupied with frequent small accidents and never looked into what serious accidents could happen. The door design was based on artificial safety that hid the latent danger. Instead, artificial safety should supplement native safety. Most Japanese think that justice finds the cause and identifies the responsible. For further accident prevention, however, cause analysis should be in the hands of other specialist organizations and justice should only come in play if necessary.