The one who slew the eight-headed serpent Yamata no Orochi was supposed to be Yamato Takeru no Mikoto (Prince Yamato Takeru), and not Susanoo no Mikoto.
The one who slew the eight-headed serpent Yamata no Orochi was Yamato Takeru no Mikoto (Yamato Takeru), and it shouldn’t have been Susanoo no Mikoto. The picture book the author was bought as a child at Okunitama Shrine in Fuchu City, Tokyo (a picture-book series from Akane Shobo, “Japanese Myths,” 6 volumes, illustrations by Suekichi Akaba, text by Katsuhiko Funazaki) was, as the author recalls, also a picture book in which Yamato Takeru no Mikoto, by getting it totally plastered drunk on sake and so on, chopped up Yamata no Orochi with a trap and defeated it, or so it should have been, but before we knew it, Volume 2, “Amano-Iwato” (The Heavenly Rock Cave), has changed to Susanoo.
This case is part of the Mandela Effect case database based on "The Window of Opportunity: A Guidepost to the Mandela Effect — The Ultra-Secret X-Files" by Aoyama Takuto.