As a fan of games with mystic setting, mythical creatures and magic, Zero End is one of my favourite AVNs and it have a huge potential to be one of the best story-driven games in mentioned style.
Writing is really solid in my opinion, it makes me really invested in plot and characters, their backstories and goals. Despite overall tone of game, it have some quite funny moments and nice romance, at least as much as it's possible for a few in-game days so far. Atmosphere in this game is great. Gloom, danger and mystery are present throughough whole game, which is exactly what I was expecting from it.
Story is really interesting and captivating with exciting lore, good amount of branching, mysteries and tension. Due to yet unanswered questions regarding MC and his old connections, game keeps me interested all the time and makes me worried during some confrontations with antagonists, as I simply don't know what to expect.
Characters are written quite well as I've already mentioned earlier, they look quite beautiful and unique, and their personalities are actually interesting without too much of cliche imo. MC is also an interesting and smart guy with some intriguing background. He's kinda edgy, but I love how characters are making fun of it, sometimes including MC himself.
Visually Zero End is pretty damn good, at least to my taste. Animations are smooth and nice as well, no complaints here from me. Models of some creatures looks actually interesting and spooky, I'd say the game have its own style with rather darker tone and mood to set the ominous atmosphere, and I love it.
Music is also on point, great choice of sounds/melodies.
There are a few small puzzles in the game, controversial ones according to some people but personally it didn't bother me at all, even if I didn't know the answer and had to spend ~30 seconds to Google them, it made me think about solution for some time and it was interesting experience nonetheless.
Overall, Zero End is an amazing game, especially if you like some supernatural stuff, old-school magic etc. and it have really big potential if dev will keep improving with future updates.