As her reward for completing the quest, Tokitate gets to ask the Game Master whether this alternate world is actually virtual or not... and the answer is that it's an alternate Earth that branched off of the original Earth's timeline. Upon hearing that it's an existing world, Yotsuya trembles with the realization that he killed real people. Once he returns to the real world and resumes his normal life, the Game Master appears before him in the form of a young girl and leads him to a meeting with the next new player.
Because I believed it was 
virtual... I was convinced...
...لأنّني اعتقدته افتراضياً... كنتُ مقتنعاً
Weil ich dachte, diese Welt
wäre virtuell … Weil ich mir sicher war …
Porque estaba convencido
de que todo era virtual…
Porque estaba convencido
de que todo era virtual…
Parce que j’étais persuadé
que c’était un monde virtuel…
Perché credevo fosse tutto virtuale...
Porque acreditei que era virtual,
estava convencido disso...
Потому что я был уверен,
что это виртуальная реальность...