How do you access the final boss in PPKP?
According to Writer Party you have to do the following steps:
Getting to the final boss is an annoying grind, but it’s simple enough to understand the method. If you want to get to the final boss, you have to beat every other boss. Load up on building materials. Go to the helicopter and move to the right side of the map, then tap on the green building. You’ll have to build something called a Mazinger Z. Then when you build it, you’ll be able to fight the final boss.