 If you liked
Gantz
|
 ...then you might like
Houkago Hokenshitsu
|
On the surface, these two seem as far off as two series can be but from the get go you'll notice how the big event that changes the protagonist's lives are similar in that they are absolutely vague, have little foreshadowing and seems to have rules that are randomly inserted.
Gantz is the more graphic series but as hard as it is to envision due to the artwork and the genre, After School Nightmare is actually the more violent series and a whole lot more important characters die in it.
In the end, it is best to treat this recommendation not as a "what do you
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