DE・JA is a Japanese-style adventure. At every screen, a menu with verb commands appears at the bottom. The commands include Examine, Talk, Ask, Take, Use (an inventory item), Move, as well as other context-specific commands that appear on some screens. Choosing a verb usually leads to an object sub-menu. Typically, the game's story advances once the player has gone through most of the commands and acquired the needed information.
The game has some scenes with nudity and mildly depicted sexual situations.