▁originally ▁titled ▁, ▁into ▁ASCII ▁Media ▁Works ' ▁ 1 7 th ▁Den ge ki ▁Nov el ▁Prize ▁in ▁ 2 0 1 0 ▁and ▁the ▁novel ▁won ▁the ▁Silver ▁Prize . ▁The ▁first ▁novel ▁was ▁published ▁by ▁ASCII ▁Media ▁Works ▁on ▁February ▁ 1 0 , ▁ 2 0 1 1 , ▁under ▁their ▁Den ge ki ▁Bun ko ▁im print , ▁and ▁ 2 0 ▁main ▁nov els , ▁two ▁pre quel ▁nov els , ▁one ▁spin - off ▁novel , ▁and ▁three ▁bonus ▁nov els ▁have ▁been ▁released ▁as ▁of ▁February ▁ 9 , ▁ 2 0 1 9 . ▁The ▁final ▁novel ▁is ▁scheduled ▁to ▁be ▁published ▁in ▁Summer ▁ 2 0 2 0 . ▁ ▁The ▁series ▁is ▁lic ensed ▁in ▁North ▁America ▁by ▁Y en ▁Press , ▁with ▁the ▁first ▁novel ▁being ▁released ▁on ▁April ▁ 2 1 , ▁ 2 0 1 5 . ▁ ▁M anga ▁A ▁m anga ▁adaptation , ▁illustrated ▁by ▁Ak io ▁H ii rag i , ▁started ▁serial ization ▁in ▁the ▁February ▁ 2 0 1 2 ▁issue ▁of ▁ASCII ▁Media ▁Works ' ▁sh ō nen ▁m anga ▁magazine ▁Den ge ki ▁Da io h . ▁The ▁first ▁tank ō bon ▁volume ▁was ▁published ▁on ▁June ▁ 2 7 , ▁ 2 0 1 2 . ▁Y en ▁Press ▁began ▁publishing ▁the ▁m anga ▁in ▁North ▁America ▁in ▁ 2 0 1 5 . ▁ ▁Sp in - off ▁A ▁spin - off ▁m anga ▁series ▁set ▁in ▁an ▁alternate ▁universe