@Kendama I'm the same person who made the previous statements. I know I'm eight months late, but I hadn't seen your comment before, and I know your the translator, so you'd likely be around.
I'll start with the easy issue of fraud. To be perfectly frank, the real-world implications of such a law, where fraud only exists once the deceived person realizes the deceit, is absolutely horrible. It would be broken as hell in real life. Here's a very basic thing. Imagine I tricked an elderly person out of their life savings in some kind of investment scheme. The elderly person dies, none the wiser. The elderly person's estate administrator finds out after doing due diligence. No crime because the person who was actually tricked never found out. You can't just say that the victim is now the administrator because the administrator doesn't have an interest in the estate (not necessarily). Imagine the administrator is just a friend of the deceased who is carrying out the will but isn't a beneficiary. Maybe the will was supposed to be that all the deceased person's belongings go to the state/government. Then the government is the victim here? Where the government has an interest in preventing something, it should just be a straight crime.
Okay, that was a lot of wordiness to get at the conclusion that there are actually real-world, legal implications to such an absolutely stupid law. Yeah, there's a philosophical component, but it goes beyond that.
As far as the other part, I stand by at least some of it. Yeah, they didn't know that it was a game to start with, but once they realized, they (well, Yamazaki, since only he could speak) should've asked more questions. Yes, he has no choice but to play. The best choice, then, would be to play WELL. Gathering information is necessary. You say that Kurose was pretty detailed? This is literally a guessing game. It's a perfectly reasonable and straightforward question to ask "what happens if I guess wrong?" Like, I get that nothing came of that issue, but it's a very logical thing to ask. It's just showing that they're not asking a lot of questions. They're being kind of passive.