This small RCA splitter was marketed in 3DO magazines in Japan. There were other items marketed with the 3DO as well, such as: headphones, microphones, and screen capturing devices.
FZ-AK1 Karaoke Mixer
The FZ-AK-1 was a Karaoke Mixer released in Japan only, later in the life of the 3DO. Not much to say about this item other than it is extremely rare and functions as a pass-through mixing microphone line-in’s and audio from the console.