For Nier, he took direct inspiration from the September 11 attacks and the War on Terror.[21][24] Another direct influence on Nier was of the gameplay of the God of War series, which both he and the game's producer Yosuke Saito admired.[25] He has stated his dislike for the "plain and forgettable" type of female video game character: he demonstrated his dislike for this and the stereotypical role-playing video game romance in Furiae, an important character in Drakengard.[4] Another character he has been greatly involved in creating is Zero, Drakengard 3's protagonist: while creating her, he felt it would be interesting to create a character who was formerly a prostitute as it was a character type that was fairly rare in video games.[26] In general, Yoko does not consider his writing to be as dark as others see it, while admitting that he deliberately incorporates dark elements.[6][27] A notable influence on the gameplay of his titles was the classic shoot 'em up Ikaruga; it directly inspired the dragon flight sequences of Drakengard and bullet hell sections in Nier; and informed Yoko on the synchronization of gameplay with the music.[28]