One delayed launch game for this system starred Takamaru, a character who'd
One delayed launch game for this system starred Takamaru, a character who'd later cameo in Captain Rainbow, on his quest to solve the titular "Riddle of Murasame Castle".  Its manufacturer used "fax stations" to allow users to send in their high scores, a feature used in the dating sim Tokimeki High School.  This system had a relatively pointless ability to be powered by C batteries, and it connected to another system via the RAM Adapter.  Its namesake data format often required flipping the games over, and it was somewhat preceded by the Data Recorder used to save levels ? in Excitebike.  The original platform for the Japanese releases of Kid Icarus, Metroid and Zelda, for 10 points, identify this add-on to the Japanese counterpart of the NES that stored games on floppy drives.
One delayed launch game for this system starred Takamaru, a character who'd later cameo in Captain Rainbow, on his quest to solve the titular "Riddle of Murasame Castle".  
{Famicom Disk} System [or {Family Computer Disc} System; I guess prompt on "{NES Disk System}" or "{Nintendo Entertainment System Disk System}"; do not accept {just} "{Famicom}" or "{NES}" or "{Nintendo Entertainment System}"]