While designing the game's RPG elements, the staff at Platinum Games were at least partially inspired by The Witcher 3: Wild Hunt in the design of their sidequests, which they felt they would never be able to match. Game designer, Takahisa Taura, said:

"When we were making the game, The Witcher 3 came out. The sub-quest elements were so great, it was kind of demoralizing, so we just stopped playing the game..."
Contributed by DrakeVagabond
The collaboration between Square Enix and Platinum Games was agreed upon with the condition that Yoko Taro relocate from Tokyo to Osaka where Platinum Games was located. Although Taro was initially uneasy about the collaboration, the staff at Platinum Games had been wanting to work on a Nier game since its release, and their enthusiasm and wish to remain faithful to the original assuaged his doubts.
Contributed by DrakeVagabond
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The game is a sequel to the stage play YoRHa that was written by the game's director, Yoko Taro. The play takes place a millennia after the events of NieR and features a cast of female androids called YoRHa.
Contributed by DrakeVagabond