I mean fail since they won’t progress if they know that it’s an illusion in the first place, which is why his hint for the others is vague
they'll get stuck then die if they realize its an illusion
They need to escape the illusion, thats the Main quest. Mc could have cleared the main quest even without brainwashing himself and already knowing that it will be illusion. But he wanted to complete the Side quest, which is about killin yourself without hesitation inside the illusion. Thats why he brainwashed himself and told others "do not fall for temptation" instead of directly saying "round 7 is about escaping illusion"
After clearing the Side quest, Mc realises that round 7 is about illusions and after that he clears the Main quest (by killing illusion of that girl)
He could have just told others that round 7 is illusion but I think he gave others vague hint because he knew that before round 7 starts, they will try to give info on round 7 to Brainwashed Black scythe and he didn't want to know that round 7 is illusion (so that he can clear side quest)
I’m a bit confused with the current mission…
Do they really kill themselves and get revived? is that how to succeed in the mission? Do they fail if they realized that it’s an illusion?