The basic premise for the manga was interesting in that it was a death game focused on being indirect. However, it felt like the author wasn't smart enough to properly utilize this premise, in that there were never really any moments where the traps, tricks, or twists were enough to shock or amaze the reader. Rather, it felt like things flailed around for most of it, and then it was resolved in a manner that was far too simplistic. There were some good moments outside of that, in terms of characterization and such, but how the fights actually went was weak. Furthermore, there was also the issue in that after the first tournament round, the manga abruptly switches into an escape room plot, where once again, it doesn't feel all that clever. In this arc too, there's strong elements and scenes in terms of the two main characters, but in terms of the puzzles it's still weak. Furthermore, there seemed to be some attempt at creating a philosophical backing to what was going on at this point, but this was somewhat nonsensical and also felt like the author was over their head. The last issue, is that the manga was very clearly axed abruptly, wherein it stops before it even gets to the second round, and hence while there was some good character growth in Nao, as the plot was barely getting started the overall the ending is completely unsatisfying. The art was really good.

tl;dr: A manga with an interesting premise but that isn't clever enough to pull it off.