This will fix the infinite loading bug when starting the game.
First, search graphics in the windows start menu. Select Graphics Settings.



Scroll down until you find DOA6.exe. If it's not there, click browse at the top of the menu, go to C:\Program Files (x86)\Steam\steamapps\common\Dead or Alive 6 and select DOA6.exe there. Then, select it and click Options.



Check Don't use optimizations for windowed games. Click save. Now launch the game and enjoy.