The software was discovered by Junkya.Hassy, a retro gamer and console repair personn Japan, who recently came into possession of two Famicom Disk System disks from a metal buying company in Kyoto that was going to throw them away. As he discovered, after loading them up, the disks contained some rare and unusual materials, including what looks to be a dev build of Hal Laboratory's Eggerland for bug fixing, as well as a mysterious undocumented game entitled Maze Ver. T2.0.
On Twitter/X, Junkya.Hassy shared a screenshot of the undocumented game in action, which features a character standing in an isometric maze full of staircases. It's not exactly known who the author of this software is at the moment, or whether it is official or not (after all, the disks were rewritable). However, given the location, the hobbyist believes that it could have potentially belonged to an employee of Nintendo or Hal Laboratory, which has people excited to know more.
He has currently loaned the disk to a friend (who is more familiar with the Famicom Disk System library) to help get to the bottom of the mystery and will post a video of its contents shortly, to demonstrate more of this mysterious piece of software.
We'll obviously try to keep an eye on this story as it develops, and will post an update if more info becomes available.