Yeah, the world of 'Demon Gaze' does expand beyond the first game! The direct sequel is 'Demon Gaze II', which continues the core dungeon-crawling mechanics and the concept of binding demons to fight for you, but it introduces a whole new cast and setting. It's set in the country of Asteria, following a rebel group, and it generally polished up a lot of the original's systems.
There's also a related title called 'Ray Gigant', which shares some staff and a similar first-person dungeon-crawler style, though it's not a direct story sequel. For those who really click with the developer's style, the 'Experience Inc.' portfolio is worth looking into—games like 'Operation Abyss' and 'Operation Babel' have a comparable vibe, even if they're separate series entirely.
If you're asking about novelizations or manga, there are some adaptations and spin-off comics, but they're usually Japan-only releases and can be tricky to track down in English. Your main, accessible follow-up is definitely the second game. I found the shift in tone and characters pretty refreshing after the first one's storyline wrapped up.
It’s not a sprawling franchise with tons of entries, so jumping into 'Demon Gaze II' feels like the natural next step if you enjoyed the original's blend of strategy and demon collection. The music and art direction in the sequel really stuck with me, too.