Based on the Golgo 13 franchise of manga, films, anime, and games, Top Secret Episode features one of the most diverse ranges of gameplay styles of any NES game. As Golgo 13, the player spends most of their time in side-scrolling action sequences in which he must kick, jumpkick and shoot his assailants as he makes his way from one meeting to the next. He is unable to duck, but can jump incredibly high.
Frequently, a hand holding a gun will appear in the foreground and fire at Golgo 13. This switches the game to a first-person sequence in which the player must blast enemies attacking Golgo 13 from 360 degrees.
The game also includes side-scrolling shooting sequences in which Golgo 13 flies a helicopter, as well as levels that take place underwater with Golgo 13 in a scuba suit and armed with a spear gun, and a series of surprisingly complex first-person mazes. The instruction booklet which accompanied the game included maps for these mazes.
There are also a few first-person sniping moments in the game, introducing the use of a scope-equipped sniper rifle. The sniping even allowed the player to aim for a headshot, another first in gaming, though it did the same amount of damage as hitting any other part of the body. Also, unlike the sniping sections of the game's follow-up, The Mafat Conspiracy, it is impossible to miss a shot.
The game's story is complex and surprisingly dialogue-heavy for an NES game, although Duke Togo remains a man of few words, and frequently responds to comments by other characters with ". . . ."
The adventure takes Duke Togo from Berlin and Greece to Rio de Janeiro and the Amazon. Although the original Japanese release involved the Nazi regime (which occasionally appears in the original manga) and even a cyborg version of Adolf Hitler, the evil organization's name was changed to DREK for the United States release, while Cyborg Hitler's name was changed to Smirk. The Swastika symbol, however, is still present in the North American release, as is Smirk's likeness to Hitler.
Top Secret Episode is also noteworthy for its inclusion of sexual subject matter. At a few times throughout the game, Duke meets with female operatives in hotel rooms, and the game depicts, from afar, Duke and the woman coming together before the lights in the room fade. In addition, the original Japanese Famicom release featured nudity, which was removed from the North American NES release.
There are several elements that managed to bypass Nintendo of America's strict censorship for the North American release, including references to drug use and smoking (which Golgo 13 does when walking over a pack of cigarettes). The blood that comes out from an enemy's head when shot in 'sniper mode' is also still visible, which was unusual for a North American NES release at the time.
In 2010, ROMhacking released an English patch that uncensors the North American release to match the original Japanese version, including the nudity as well as the Nazi and Hitler references.