Ninja Gaiden 2: Easter Egg - DOA4 Reference

In the game’s third chapter, you will be on the streets of New York. Near the beginning of the chapter, you will drop down into a sewer and fight there for a while. When you reemerge back on the streets from your brief sewer battle, an alley with a treasure chest at the end of it can be found. Right next to the chest is a building that says DOATEC in huge letters. DOATEC is the evil corporation that you do battle against in another Tecmo game, Dead or Alive 4.