I love horror, and this piqued my interest due the similarity to the concept of Event Horizon. Unfortunately, the plot becomes a mess once the supernatural bit kicks in, and a lot of panels were too dark to even tell what was going on. The ending feels rushed, and I would've gladly spared some of the technobabble for more character development moments.
Some characters, like Nozomi and Meilin, speak and act in ways that don't make sense considering the situation and their previously established traits. Meilin and Herschbach had potential, but aren't given much time to be anything but plot devices. All Nozomi does 90% of the time is antagonize Kengo for no good reason; he is neither likeable nor interesting, yet is given a big heroic moment at the end because he got a name and more panels than the rest. Kengo himself is a forgettable lead and, while everyone else displays skills in their respective fields, I kept wondering why he was even brought onto the project. Is he a mechanic? An engineer? A scientist? Who knows. As the audience avatar, he mostly runs around yelling at others and looking stressed. At least Miwa was fairly interesting, and by far the most developed character.
The story would've greatly benefited from a "less is more" approach, with the supernatural aspect dialed down a bit as the characters investigate, until the climax. All of it — the shady Chinese company, the Aztec god, the Chinese military wanting to gain control of the Aztec god and use it as a weapon (glossed over in like 3 panels, lol) — ended up being a jumbled mess. That's not even mentioning the contrivances, like how the counselor conveniently knows all about Aztec codices, or how all the information reaches everyone despite characters (whom we're following in real time) not being shown talking about it.
It feels like Koike was held back by the necessity to give screen time to every mildly important character and develop a supernatural plot at the same time. There are quite a few contrivances in the writing, and the art would've been great had some of that black ink been spared. As the end drew near, I realized that I didn't really care whether any of the characters lived or died, which is a pity when you're supposed to be rooting for them. It's an interesting concept, but, eh — not as well done in 4 volumes as Event Horizon managed to do in little over 1.5 hours.