While Atlus is the video game company that is most often associated with Megami Tensei today, it's important to note it wasn't the first to try and adapt Aya Nishitani's Digital Devil Story novels into an interactive medium.
That honour instead belongs to the company Telenet Japan who, in 1987, beat Atlus to the punch by releasing its own game titled Digital Devil Monogatari: Megami Tensei for Japanese home computers.
This version of the game is vastly different from the Atlus title that was eventually released for the Nintendo Famicom later that same year, being much more of an action RPG than a dungeon crawler. However, one thing it does share in common with the Atlus version is that it was also only ever released in Japan, making it difficult for those with very little knowledge of Japanese to understand.
Now, though, thanks to fans, it's finally possible to play the game with English text (the Famicom version got its own translation back in 2018), with the MSX release receiving a brand new patch from Kaisaan Siddiqui and a group of other translators/hackers (thanks gamevecanti for the spot!).
If you want to try it out, you can download the patch now from romhacking.net.