@Kaarme
Everyone is commenting about how could anyone have foreseen this, how they should've guessed but teens in this world get into drugs, unsafe sex, smoke, drink while knowing the dangers.
It is a well known fact that teenagers are dumb, they wanted to have fun, they just didn't really consider the risks.
Plus if you noticed Art's dialogue phrasing it seemed like the book was a popular play thing. Meaning many people must've gone into the rpg and been perfectly alright. It seems magic books aren't supposed to develop a personality like this one. Meaning an anomaly.
And again there was a failsafe. The emblem they drew. It just didn't work for Lycoris because she is the equivalent of a yandere magnet who simultaneously increases yandereness and decreases it.
Username is sarcasm.