Kagerou Daze, Vol. 1 (manga‪)‬

This is the story of August 14 and 15.
Shintaro Kisaragi--self-appointed guardian of his domestic domain--has refused to leave the comfort of his room for two whole years. But Shintaro's life is about to take an unexpected turn when his computer crashes and he is forced to venture into the world he was happy to shut out forever...and stumbles right into the middle of a hostage situation!