Thought only Tecmo's Team Ninja were the masters of in-game boob physics? Ha! Japanese game developers AC Gateway and Gadgetsoft seem to have invested a lot of energy into perfecting boob physics.
In new PSP title Masquerade Maid Guy: Bouncing Battle Royale, the devs used what they're calling the Super Tayunizm Engine — basically, a boob-bounce-making game engine. There are tech demos after the jump in both 2D and 3D. Enlightening.