Well, I finished playing through the demo last night. I took many, many notes.
The setting, plot, and characters seem interesting, though not much has yet been revealed about Durchhalten. I'm looking forward to seeing you plumb their emotional depths. (Eiji is my favorite by far.)
The art and user interface are top-notch---I liked that the backgrounds weren't static. That sign in Eiji's bar made my jaw drop.
You've already heard my suggestion regarding the first puzzle, but I ran into more trouble later that could be easily solved with a quick prompt.
I spent several minutes clicking on the biochip before I figured out what exactly I was meant to click. Please provide some indication of what to do in your puzzles. By the time I reached the radio, however, you seemed to have learned this lesson, because Yu told me when I was clicking on the buttons in the incorrect order.
The writing, unfortunately, simply doesn't measure up overall. It was as if I read work from two distinctly different people---one with a penchant for snappy dialogue and one who needs to rewrite his first draft.
I noticed your garden variety typos, missing words, and grammatical problems, but two things in particular have me worried. The text often switched tenses, as shown here:
"“Yu traversed the dark streets of Akihabara, noticing as he gets closer to the city's center that there are more people walking around in Novus Tokyo now than a few years ago.”
You need to decide whether Yu traversed the streets or traverses them. If you're describing everything Yu experiences in the present tense, stick with the present tense. If you're using the immediate past tense, make sure you don't deviate from it (unless of course you have to use future tense in dialogue, etc.).
The other issue is much larger in scope and is officially my primary concern. Throughout the demo, I encountered spates of over-description and poorly structured sentences. Sometimes I had to take a break from reading in order to figure out was being said or described. There is such a thing as too much detail, or detail poorly implemented. Details and descriptions should enhance the text, not weigh it down until it becomes a bloated, plodding mess. A visual novel is still a novel, and I can tell you that any publishers worth their salt will not publish a book in this state, no matter how pretty the dust jacket is.
“Yu looked at the screen of the homemade device his group used for telecommunication. The caller, unsurprisingly, was the girl Midori who's the only one other than Toshio who always kept in touch with him after the Durchhalten fell apart.”
Possible rewrite: "Yu glanced at his homemade telecommunicator. Midori was calling. Not surprising at all, he thought. After the Durchhalten fell apart, she and Toshio were the only ones who kept in touch with him."
“In a world where survival of the fittest ruled, he could not hold a grudge. He succumbed to the predators and slowly faded away, his last thoughts being that of his sister whom he'll never see again.”
Possible rewrite: "Survival of the fittest, Yu thought ruefully. He would never see Miho again."
“Yu could not shake off the dumbfounding feeling he had as he looked at the girl's peculiar dress.”
Possible rewrite: "Yu was dumbfounded. What was she wearing?"
“The other man just grumbled incomprehensibly as he seemingly conceded, handing over to his drinking buddy the chip and tools needed to modify it.”
Possible rewrite: "Nobu grunted and gave Haru the chip."
“I see a stranger whose arms are covered with scabs---dark crusts of temporary skin indicative of healing wounds.”
Possible rewrite: "I see a stranger whose arms are covered with scabs." (Everyone knows what a scab is!)
“Yu did not say anything, nor did he think Eiji's query warranted a reply. He did have a gut feeling that the event struck Eiji to the core. Could it have been purely an emotional response to a tragedy that kept Eiji mum? Yu kept to himself as he tried to find an answer in his mind.”
Possible rewrite: "Yu was silent. Eiji's question didn't deserve an answer."
The main thing to remember about description is to show, not tell. And less is usually more. I know this post sounds harsh, but I have to speak up, especially since this project is promising in all other respects. If I let the writing stay as it is, I'd hate myself.