Dragon Head, Hyouryuu Kyoushitsu Recommendations
They both have apocaliptic settings and a world mostly completly covered in darkness.
If I were to pick one manga that was the biggest influence on Dragon Head it would be The Drifting Classroom (Hyouryuu Kyoushitsu). Both involve students trapped in an apocalyptic setting and having to deal with a new world they neither understand nor enjoy.
Dragon Head is scarier than The Drifting Classroom, and has a more ambiguous plot, however they both mine similar territory when it comes to generating fear. Both also take inspiration and influence from Lord of the Flies.