The criminal trade organization WWWF was finally defeated. The bionic soldier Blon-Win is appointed a high-ranked inspector and sent on a mission to protect the secret service agent Remi Binderk on the way to the United Nations conference in Geneva. On board the TGV train in France Blon-Win encounters her old acquaintance Dalzy, who tells her that former WWWF members have united to form the Einheit group, and are working on a new dangerous weapon known as G-R. D-Again is the fifth entry in The 4th Unit series and a sequel to Zerø. Gameplay-wise, it retains most elements introduced in the previous games. There are more context-specific commands and relative freedom of movement compared to the immediate predecessor. New commands include actions such as drinking and eating. Four emotional stances (nice, angry, sad, and surprised) are present. However, it is no longer possible to choose topics during dialogues. Like in the preceding game, Blon-Win can choose to attack any character at any time, and the simple turn-based combat mechanics of the series have been preserved.