One unspecified day, Issei finds himself in a room with other strangers. Death himself arrives and forces them to play a game to redeem their souls. What have these people done to end up in this limbo of deadly games?

Our hero Issei, receives a gun from his dying grandfather and becomes a hitman with it. A monster killing agency later takes him into custody after seeing Issei's skills. Our hero then gets trained to fight monsters, learning more about his grandfather's past and how the magic guns work in this f...

It started with a full moon... Issei, one day sees a girl walking on air outside his window. He falls in love at first sight. The girl invites him to play together and from there the two become friends and then maybe even lovers.