Superhuman is unique in a lot of ways. I suspect you wouldn't find a game quite like it even if you played every single game on this site, but there are other titles that are of similar quality at least in certain aspects.
The two games that feel most similar to SH to me are
Zero End (which sounds like it could be the game Sidartha_6 was trying to think of) and
Demons of the Hearth. Both of them feature excellent and deep worldbuilding, interesting plots, competing factions, characters with their own lives and sets of interests, high quality fight scenes, and dark atmospheres. Several of my pals in the Superhuman community really like Zero End so it'd probably be the one I'd most recommend to you if you haven't played it yet.
Then there are two series that also have really good fantasy worldbuilding and excellent characters but are quite different from Superhuman in tone:
Mythos and the Elsaverse (you'll probably want to start with the
Omnibus). Mythos is a murder mystery and a comedy and tends to be a fair bit lighter than Superhuman. The Elsaverse games and stories, though quite varied, focus more on relationships and romance than Superhuman does. In addition, neither Mythos nor the Elsaverse emphasize fight scenes. Another thing they both have in common with Superhuman is that they also have generally nontoxic and supportive fanbases which makes their game threads much more pleasant to read.
There are also a few games that remind me of Superhuman mostly because of their fight scenes.
Tokyo Babel is an all-ages VN set in a world where angels and demons coexist. The worldbuilding and story are actually quite interesting, but the fight scenes are particularly well-done (among the best-written I've ever seen in a VN though still not quite on Superhuman's level) and the opponents are all quite unique. However, choices are few and far between so there is much less of a feeling that you're actually affecting the story with your own actions and you can't really roleplay the MC in your own way. In addition, the most interesting LI in my opinion can only be pursued after you play the other routes which isn't a mechanic I'm fond of at all. There are others on this thread who are far more knowledgeable about it than I am, but
Mad World also has good fight scenes. I'll also throw
Alpha Omega into this category because combat seems like it will be an important aspect of the gameplay. The MC is training to become a competitive fighter so the stakes are a fair bit lower than in Superhuman (though one character has already been seriously injured in a fight). The characters are well-written and the story manages to be both entertaining and have real emotional impact. Given the competitive combat setting, some of the LIs are quite muscular and don't have the typical Daz look which could very well appeal to Superhuman fans.
Finally, I'll mention
Nothing Is Forever and
Leaving DNA because of the high quality of the writing and the depth of the characters. They are grounded and realistic VNs so they won't scratch that itch for adventure and fantasy that Superhuman and most of the other games I've mentioned here do, but if you love Superhuman you love a great story and these are two of the very best you'll find here. Granted, I might be the only person on this site who actually counts Superhuman, Nothing Is Forever, and Leaving DNA as my three favorite AVNs, but I urge you to give them a chance. Nothing Is Forever even has RPG-like stats and skills and you have a lot of freedom to play the MC as you see fit, including by making choices that could be considered evil. (Admittedly, you can't go full murderhobo...not yet, anyway!)
I'm really glad it worked out in that regards. 
