I gotta congratulate Vivid Dead for making me use CheatEngine for the first time in my life lol. The funniest part is that even with that, the clunky controls, puzzles and map layout (with no actual MAP to look at) still make this game very challenging. There were also a few places in the Tower of Mist where I'm pretty sure I received 100+ damage in a single hit, resulting in a game over before CheatEngine was even able to reset my HP back to 100
If this developer seriously intends to release this on Steam with the current level of difficulty, the game is gonna get torn apart in the reviews there. In my playthrough it felt like I was traversing the developer's sadistic mind rather than traversing levels in a video game. Even the paltry "reward" at the top of the tower will require most players to browse forums on how to actually activate it after going through hell to reach it, jeez!
TLDR: The only other hentai game I can remember that even remotely approaches Vivid Dead's difficulty is Gorepete's "Sakyubasu No Tatakai II", and I'm pretty sure that one is still significantly easier to beat overall.