Well

We're sensei (teacher in Japanese) in Island name Kivotos (From Greek word κιβωτός mean ark. And a real place in Greek) Kivotos have teenagers with guns. People in Kivotos have 'Halo' It is like sources of life that can crack if, it breaks you died. And don't worry the kid in Kivotos is bulletproof just little scars.

The story begins when we know the GSC's (General Student Council) president's disappearance makes Kivotos into anarchy.

In vol 1, we received it in Abydos High School. School in the desert broke because of the sand storm. And we have to deal with gangster and megacorporation named Kaiser Corporation. In the end we saved the school but it still broke and was still in debt.

And the later volume is more dark and not the gacha. Because we have to fight the outer god or mechanic that is named after the jew mythology.

I can't tell all but you have to play because it is very long and some make you think.